POJ 3126：Prime Path

Prime Path

Time Limit: 1000MS

Memory Limit: 65536KB

64bit IO Format: %I64d & %I64u

Submit Status

Description

The ministers of the cabinet were quite upset by the message from the Chief of Security stating that they would all have to change the four-digit room numbers
on their offices. 

— It is a matter of security to change such things every now and then, to keep the enemy in the dark. 

— But look, I have chosen my number 1033 for good reasons. I am the Prime minister, you know! 

— I know, so therefore your new number 8179 is also a prime. You will just have to paste four new digits over the four old ones on your office door. 

— No, it’s not that simple. Suppose that I change the first digit to an 8, then the number will read 8033 which is not a prime! 

— I see, being the prime minister you cannot stand having a non-prime number on your door even for a few seconds. 

— Correct! So I must invent a scheme for going from 1033 to 8179 by a path of prime numbers where only one digit is changed from one prime to the next prime. 



Now, the minister of finance, who had been eavesdropping, intervened. 

— No unnecessary expenditure, please! I happen to know that the price of a digit is one pound. 

— Hmm, in that case I need a computer program to minimize the cost. You don't know some very cheap software gurus, do you? 

— In fact, I do. You see, there is this programming contest going on... Help the prime minister to find the cheapest prime path between any two given four-digit primes! The first digit must be nonzero, of course. Here is a solution in the case above.

1033 

1733 

3733 

3739 

3779 

8779 

8179

The cost of this solution is 6 pounds. Note that the digit 1 which got pasted over in step 2 can not be reused in the last step – a new 1 must be purchased.

Input

One line with a positive number: the number of test cases (at most 100). Then for each test case, one line with two numbers separated by a blank. Both numbers are four-digit primes (without leading zeros).

Output

One line for each case, either with a number stating the minimal cost or containing the word Impossible.

Sample Input

3
1033 8179
1373 8017
1033 1033

Sample Output

6
7
0

题意是给两个质数a和b，每次只能变a中的一位，且变完后的a也要是一个质数，问经过多少次变换能变成b。

广度优先搜索很典型了，只是还是觉得自己这样做比较麻烦，把a每一次能到达的数a‘弄到queue里面。只是一开始a'的判断TLE了，觉得是每次判断是不是质数浪费了时间。所以把从1000到10000的质数全都列了出来，这样不用一个一个判断了，在里面就是质数，不在里面就out。

我觉得其他人肯定有更好的方法，自己还是要好好学习。

代码：

#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <queue>
#include <cstring>
#pragma warning(disable:4996)
using namespace std;

queue <int> q;
int ans[10005];
int a[1065];

bool pend(int b)
{
	int i;
	for(i=0;i<=1060;i++)
	{
		if(b==a[i])
			return true;
	}
	return false;
}

int main()
{
	a[0]=1009;
	a[1]=1013;
	a[2]=1019;
	a[3]=1021;
	a[4]=1031;
	a[5]=1033;
	a[6]=1039;
	a[7]=1049;
	a[8]=1051;
	a[9]=1061;
	a[10]=1063;
	a[11]=1069;
	a[12]=1087;
	a[13]=1091;
	a[14]=1093;
	a[15]=1097;
	a[16]=1103;
	a[17]=1109;
	a[18]=1117;
	a[19]=1123;
	a[20]=1129;
	a[21]=1151;
	a[22]=1153;
	a[23]=1163;
	a[24]=1171;
	a[25]=1181;
	a[26]=1187;
	a[27]=1193;
	a[28]=1201;
	a[29]=1213;
	a[30]=1217;
	a[31]=1223;
	a[32]=1229;
	a[33]=1231;
	a[34]=1237;
	a[35]=1249;
	a[36]=1259;
	a[37]=1277;
	a[38]=1279;
	a[39]=1283;
	a[40]=1289;
	a[41]=1291;
	a[42]=1297;
	a[43]=1301;
	a[44]=1303;
	a[45]=1307;
	a[46]=1319;
	a[47]=1321;
	a[48]=1327;
	a[49]=1361;
	a[50]=1367;
	a[51]=1373;
	a[52]=1381;
	a[53]=1399;
	a[54]=1409;
	a[55]=1423;
	a[56]=1427;
	a[57]=1429;
	a[58]=1433;
	a[59]=1439;
	a[60]=1447;
	a[61]=1451;
	a[62]=1453;
	a[63]=1459;
	a[64]=1471;
	a[65]=1481;
	a[66]=1483;
	a[67]=1487;
	a[68]=1489;
	a[69]=1493;
	a[70]=1499;
	a[71]=1511;
	a[72]=1523;
	a[73]=1531;
	a[74]=1543;
	a[75]=1549;
	a[76]=1553;
	a[77]=1559;
	a[78]=1567;
	a[79]=1571;
	a[80]=1579;
	a[81]=1583;
	a[82]=1597;
	a[83]=1601;
	a[84]=1607;
	a[85]=1609;
	a[86]=1613;
	a[87]=1619;
	a[88]=1621;
	a[89]=1627;
	a[90]=1637;
	a[91]=1657;
	a[92]=1663;
	a[93]=1667;
	a[94]=1669;
	a[95]=1693;
	a[96]=1697;
	a[97]=1699;
	a[98]=1709;
	a[99]=1721;
	a[100]=1723;
	a[101]=1733;
	a[102]=1741;
	a[103]=1747;
	a[104]=1753;
	a[105]=1759;
	a[106]=1777;
	a[107]=1783;
	a[108]=1787;
	a[109]=1789;
	a[110]=1801;
	a[111]=1811;
	a[112]=1823;
	a[113]=1831;
	a[114]=1847;
	a[115]=1861;
	a[116]=1867;
	a[117]=1871;
	a[118]=1873;
	a[119]=1877;
	a[120]=1879;
	a[121]=1889;
	a[122]=1901;
	a[123]=1907;
	a[124]=1913;
	a[125]=1931;
	a[126]=1933;
	a[127]=1949;
	a[128]=1951;
	a[129]=1973;
	a[130]=1979;
	a[131]=1987;
	a[132]=1993;
	a[133]=1997;
	a[134]=1999;
	a[135]=2003;
	a[136]=2011;
	a[137]=2017;
	a[138]=2027;
	a[139]=2029;
	a[140]=2039;
	a[141]=2053;
	a[142]=2063;
	a[143]=2069;
	a[144]=2081;
	a[145]=2083;
	a[146]=2087;
	a[147]=2089;
	a[148]=2099;
	a[149]=2111;
	a[150]=2113;
	a[151]=2129;
	a[152]=2131;
	a[153]=2137;
	a[154]=2141;
	a[155]=2143;
	a[156]=2153;
	a[157]=2161;
	a[158]=2179;
	a[159]=2203;
	a[160]=2207;
	a[161]=2213;
	a[162]=2221;
	a[163]=2237;
	a[164]=2239;
	a[165]=2243;
	a[166]=2251;
	a[167]=2267;
	a[168]=2269;
	a[169]=2273;
	a[170]=2281;
	a[171]=2287;
	a[172]=2293;
	a[173]=2297;
	a[174]=2309;
	a[175]=2311;
	a[176]=2333;
	a[177]=2339;
	a[178]=2341;
	a[179]=2347;
	a[180]=2351;
	a[181]=2357;
	a[182]=2371;
	a[183]=2377;
	a[184]=2381;
	a[185]=2383;
	a[186]=2389;
	a[187]=2393;
	a[188]=2399;
	a[189]=2411;
	a[190]=2417;
	a[191]=2423;
	a[192]=2437;
	a[193]=2441;
	a[194]=2447;
	a[195]=2459;
	a[196]=2467;
	a[197]=2473;
	a[198]=2477;
	a[199]=2503;
	a[200]=2521;
	a[201]=2531;
	a[202]=2539;
	a[203]=2543;
	a[204]=2549;
	a[205]=2551;
	a[206]=2557;
	a[207]=2579;
	a[208]=2591;
	a[209]=2593;
	a[210]=2609;
	a[211]=2617;
	a[212]=2621;
	a[213]=2633;
	a[214]=2647;
	a[215]=2657;
	a[216]=2659;
	a[217]=2663;
	a[218]=2671;
	a[219]=2677;
	a[220]=2683;
	a[221]=2687;
	a[222]=2689;
	a[223]=2693;
	a[224]=2699;
	a[225]=2707;
	a[226]=2711;
	a[227]=2713;
	a[228]=2719;
	a[229]=2729;
	a[230]=2731;
	a[231]=2741;
	a[232]=2749;
	a[233]=2753;
	a[234]=2767;
	a[235]=2777;
	a[236]=2789;
	a[237]=2791;
	a[238]=2797;
	a[239]=2801;
	a[240]=2803;
	a[241]=2819;
	a[242]=2833;
	a[243]=2837;
	a[244]=2843;
	a[245]=2851;
	a[246]=2857;
	a[247]=2861;
	a[248]=2879;
	a[249]=2887;
	a[250]=2897;
	a[251]=2903;
	a[252]=2909;
	a[253]=2917;
	a[254]=2927;
	a[255]=2939;
	a[256]=2953;
	a[257]=2957;
	a[258]=2963;
	a[259]=2969;
	a[260]=2971;
	a[261]=2999;
	a[262]=3001;
	a[263]=3011;
	a[264]=3019;
	a[265]=3023;
	a[266]=3037;
	a[267]=3041;
	a[268]=3049;
	a[269]=3061;
	a[270]=3067;
	a[271]=3079;
	a[272]=3083;
	a[273]=3089;
	a[274]=3109;
	a[275]=3119;
	a[276]=3121;
	a[277]=3137;
	a[278]=3163;
	a[279]=3167;
	a[280]=3169;
	a[281]=3181;
	a[282]=3187;
	a[283]=3191;
	a[284]=3203;
	a[285]=3209;
	a[286]=3217;
	a[287]=3221;
	a[288]=3229;
	a[289]=3251;
	a[290]=3253;
	a[291]=3257;
	a[292]=3259;
	a[293]=3271;
	a[294]=3299;
	a[295]=3301;
	a[296]=3307;
	a[297]=3313;
	a[298]=3319;
	a[299]=3323;
	a[300]=3329;
	a[301]=3331;
	a[302]=3343;
	a[303]=3347;
	a[304]=3359;
	a[305]=3361;
	a[306]=3371;
	a[307]=3373;
	a[308]=3389;
	a[309]=3391;
	a[310]=3407;
	a[311]=3413;
	a[312]=3433;
	a[313]=3449;
	a[314]=3457;
	a[315]=3461;
	a[316]=3463;
	a[317]=3467;
	a[318]=3469;
	a[319]=3491;
	a[320]=3499;
	a[321]=3511;
	a[322]=3517;
	a[323]=3527;
	a[324]=3529;
	a[325]=3533;
	a[326]=3539;
	a[327]=3541;
	a[328]=3547;
	a[329]=3557;
	a[330]=3559;
	a[331]=3571;
	a[332]=3581;
	a[333]=3583;
	a[334]=3593;
	a[335]=3607;
	a[336]=3613;
	a[337]=3617;
	a[338]=3623;
	a[339]=3631;
	a[340]=3637;
	a[341]=3643;
	a[342]=3659;
	a[343]=3671;
	a[344]=3673;
	a[345]=3677;
	a[346]=3691;
	a[347]=3697;
	a[348]=3701;
	a[349]=3709;
	a[350]=3719;
	a[351]=3727;
	a[352]=3733;
	a[353]=3739;
	a[354]=3761;
	a[355]=3767;
	a[356]=3769;
	a[357]=3779;
	a[358]=3793;
	a[359]=3797;
	a[360]=3803;
	a[361]=3821;
	a[362]=3823;
	a[363]=3833;
	a[364]=3847;
	a[365]=3851;
	a[366]=3853;
	a[367]=3863;
	a[368]=3877;
	a[369]=3881;
	a[370]=3889;
	a[371]=3907;
	a[372]=3911;
	a[373]=3917;
	a[374]=3919;
	a[375]=3923;
	a[376]=3929;
	a[377]=3931;
	a[378]=3943;
	a[379]=3947;
	a[380]=3967;
	a[381]=3989;
	a[382]=4001;
	a[383]=4003;
	a[384]=4007;
	a[385]=4013;
	a[386]=4019;
	a[387]=4021;
	a[388]=4027;
	a[389]=4049;
	a[390]=4051;
	a[391]=4057;
	a[392]=4073;
	a[393]=4079;
	a[394]=4091;
	a[395]=4093;
	a[396]=4099;
	a[397]=4111;
	a[398]=4127;
	a[399]=4129;
	a[400]=4133;
	a[401]=4139;
	a[402]=4153;
	a[403]=4157;
	a[404]=4159;
	a[405]=4177;
	a[406]=4201;
	a[407]=4211;
	a[408]=4217;
	a[409]=4219;
	a[410]=4229;
	a[411]=4231;
	a[412]=4241;
	a[413]=4243;
	a[414]=4253;
	a[415]=4259;
	a[416]=4261;
	a[417]=4271;
	a[418]=4273;
	a[419]=4283;
	a[420]=4289;
	a[421]=4297;
	a[422]=4327;
	a[423]=4337;
	a[424]=4339;
	a[425]=4349;
	a[426]=4357;
	a[427]=4363;
	a[428]=4373;
	a[429]=4391;
	a[430]=4397;
	a[431]=4409;
	a[432]=4421;
	a[433]=4423;
	a[434]=4441;
	a[435]=4447;
	a[436]=4451;
	a[437]=4457;
	a[438]=4463;
	a[439]=4481;
	a[440]=4483;
	a[441]=4493;
	a[442]=4507;
	a[443]=4513;
	a[444]=4517;
	a[445]=4519;
	a[446]=4523;
	a[447]=4547;
	a[448]=4549;
	a[449]=4561;
	a[450]=4567;
	a[451]=4583;
	a[452]=4591;
	a[453]=4597;
	a[454]=4603;
	a[455]=4621;
	a[456]=4637;
	a[457]=4639;
	a[458]=4643;
	a[459]=4649;
	a[460]=4651;
	a[461]=4657;
	a[462]=4663;
	a[463]=4673;
	a[464]=4679;
	a[465]=4691;
	a[466]=4703;
	a[467]=4721;
	a[468]=4723;
	a[469]=4729;
	a[470]=4733;
	a[471]=4751;
	a[472]=4759;
	a[473]=4783;
	a[474]=4787;
	a[475]=4789;
	a[476]=4793;
	a[477]=4799;
	a[478]=4801;
	a[479]=4813;
	a[480]=4817;
	a[481]=4831;
	a[482]=4861;
	a[483]=4871;
	a[484]=4877;
	a[485]=4889;
	a[486]=4903;
	a[487]=4909;
	a[488]=4919;
	a[489]=4931;
	a[490]=4933;
	a[491]=4937;
	a[492]=4943;
	a[493]=4951;
	a[494]=4957;
	a[495]=4967;
	a[496]=4969;
	a[497]=4973;
	a[498]=4987;
	a[499]=4993;
	a[500]=4999;
	a[501]=5003;
	a[502]=5009;
	a[503]=5011;
	a[504]=5021;
	a[505]=5023;
	a[506]=5039;
	a[507]=5051;
	a[508]=5059;
	a[509]=5077;
	a[510]=5081;
	a[511]=5087;
	a[512]=5099;
	a[513]=5101;
	a[514]=5107;
	a[515]=5113;
	a[516]=5119;
	a[517]=5147;
	a[518]=5153;
	a[519]=5167;
	a[520]=5171;
	a[521]=5179;
	a[522]=5189;
	a[523]=5197;
	a[524]=5209;
	a[525]=5227;
	a[526]=5231;
	a[527]=5233;
	a[528]=5237;
	a[529]=5261;
	a[530]=5273;
	a[531]=5279;
	a[532]=5281;
	a[533]=5297;
	a[534]=5303;
	a[535]=5309;
	a[536]=5323;
	a[537]=5333;
	a[538]=5347;
	a[539]=5351;
	a[540]=5381;
	a[541]=5387;
	a[542]=5393;
	a[543]=5399;
	a[544]=5407;
	a[545]=5413;
	a[546]=5417;
	a[547]=5419;
	a[548]=5431;
	a[549]=5437;
	a[550]=5441;
	a[551]=5443;
	a[552]=5449;
	a[553]=5471;
	a[554]=5477;
	a[555]=5479;
	a[556]=5483;
	a[557]=5501;
	a[558]=5503;
	a[559]=5507;
	a[560]=5519;
	a[561]=5521;
	a[562]=5527;
	a[563]=5531;
	a[564]=5557;
	a[565]=5563;
	a[566]=5569;
	a[567]=5573;
	a[568]=5581;
	a[569]=5591;
	a[570]=5623;
	a[571]=5639;
	a[572]=5641;
	a[573]=5647;
	a[574]=5651;
	a[575]=5653;
	a[576]=5657;
	a[577]=5659;
	a[578]=5669;
	a[579]=5683;
	a[580]=5689;
	a[581]=5693;
	a[582]=5701;
	a[583]=5711;
	a[584]=5717;
	a[585]=5737;
	a[586]=5741;
	a[587]=5743;
	a[588]=5749;
	a[589]=5779;
	a[590]=5783;
	a[591]=5791;
	a[592]=5801;
	a[593]=5807;
	a[594]=5813;
	a[595]=5821;
	a[596]=5827;
	a[597]=5839;
	a[598]=5843;
	a[599]=5849;
	a[600]=5851;
	a[601]=5857;
	a[602]=5861;
	a[603]=5867;
	a[604]=5869;
	a[605]=5879;
	a[606]=5881;
	a[607]=5897;
	a[608]=5903;
	a[609]=5923;
	a[610]=5927;
	a[611]=5939;
	a[612]=5953;
	a[613]=5981;
	a[614]=5987;
	a[615]=6007;
	a[616]=6011;
	a[617]=6029;
	a[618]=6037;
	a[619]=6043;
	a[620]=6047;
	a[621]=6053;
	a[622]=6067;
	a[623]=6073;
	a[624]=6079;
	a[625]=6089;
	a[626]=6091;
	a[627]=6101;
	a[628]=6113;
	a[629]=6121;
	a[630]=6131;
	a[631]=6133;
	a[632]=6143;
	a[633]=6151;
	a[634]=6163;
	a[635]=6173;
	a[636]=6197;
	a[637]=6199;
	a[638]=6203;
	a[639]=6211;
	a[640]=6217;
	a[641]=6221;
	a[642]=6229;
	a[643]=6247;
	a[644]=6257;
	a[645]=6263;
	a[646]=6269;
	a[647]=6271;
	a[648]=6277;
	a[649]=6287;
	a[650]=6299;
	a[651]=6301;
	a[652]=6311;
	a[653]=6317;
	a[654]=6323;
	a[655]=6329;
	a[656]=6337;
	a[657]=6343;
	a[658]=6353;
	a[659]=6359;
	a[660]=6361;
	a[661]=6367;
	a[662]=6373;
	a[663]=6379;
	a[664]=6389;
	a[665]=6397;
	a[666]=6421;
	a[667]=6427;
	a[668]=6449;
	a[669]=6451;
	a[670]=6469;
	a[671]=6473;
	a[672]=6481;
	a[673]=6491;
	a[674]=6521;
	a[675]=6529;
	a[676]=6547;
	a[677]=6551;
	a[678]=6553;
	a[679]=6563;
	a[680]=6569;
	a[681]=6571;
	a[682]=6577;
	a[683]=6581;
	a[684]=6599;
	a[685]=6607;
	a[686]=6619;
	a[687]=6637;
	a[688]=6653;
	a[689]=6659;
	a[690]=6661;
	a[691]=6673;
	a[692]=6679;
	a[693]=6689;
	a[694]=6691;
	a[695]=6701;
	a[696]=6703;
	a[697]=6709;
	a[698]=6719;
	a[699]=6733;
	a[700]=6737;
	a[701]=6761;
	a[702]=6763;
	a[703]=6779;
	a[704]=6781;
	a[705]=6791;
	a[706]=6793;
	a[707]=6803;
	a[708]=6823;
	a[709]=6827;
	a[710]=6829;
	a[711]=6833;
	a[712]=6841;
	a[713]=6857;
	a[714]=6863;
	a[715]=6869;
	a[716]=6871;
	a[717]=6883;
	a[718]=6899;
	a[719]=6907;
	a[720]=6911;
	a[721]=6917;
	a[722]=6947;
	a[723]=6949;
	a[724]=6959;
	a[725]=6961;
	a[726]=6967;
	a[727]=6971;
	a[728]=6977;
	a[729]=6983;
	a[730]=6991;
	a[731]=6997;
	a[732]=7001;
	a[733]=7013;
	a[734]=7019;
	a[735]=7027;
	a[736]=7039;
	a[737]=7043;
	a[738]=7057;
	a[739]=7069;
	a[740]=7079;
	a[741]=7103;
	a[742]=7109;
	a[743]=7121;
	a[744]=7127;
	a[745]=7129;
	a[746]=7151;
	a[747]=7159;
	a[748]=7177;
	a[749]=7187;
	a[750]=7193;
	a[751]=7207;
	a[752]=7211;
	a[753]=7213;
	a[754]=7219;
	a[755]=7229;
	a[756]=7237;
	a[757]=7243;
	a[758]=7247;
	a[759]=7253;
	a[760]=7283;
	a[761]=7297;
	a[762]=7307;
	a[763]=7309;
	a[764]=7321;
	a[765]=7331;
	a[766]=7333;
	a[767]=7349;
	a[768]=7351;
	a[769]=7369;
	a[770]=7393;
	a[771]=7411;
	a[772]=7417;
	a[773]=7433;
	a[774]=7451;
	a[775]=7457;
	a[776]=7459;
	a[777]=7477;
	a[778]=7481;
	a[779]=7487;
	a[780]=7489;
	a[781]=7499;
	a[782]=7507;
	a[783]=7517;
	a[784]=7523;
	a[785]=7529;
	a[786]=7537;
	a[787]=7541;
	a[788]=7547;
	a[789]=7549;
	a[790]=7559;
	a[791]=7561;
	a[792]=7573;
	a[793]=7577;
	a[794]=7583;
	a[795]=7589;
	a[796]=7591;
	a[797]=7603;
	a[798]=7607;
	a[799]=7621;
	a[800]=7639;
	a[801]=7643;
	a[802]=7649;
	a[803]=7669;
	a[804]=7673;
	a[805]=7681;
	a[806]=7687;
	a[807]=7691;
	a[808]=7699;
	a[809]=7703;
	a[810]=7717;
	a[811]=7723;
	a[812]=7727;
	a[813]=7741;
	a[814]=7753;
	a[815]=7757;
	a[816]=7759;
	a[817]=7789;
	a[818]=7793;
	a[819]=7817;
	a[820]=7823;
	a[821]=7829;
	a[822]=7841;
	a[823]=7853;
	a[824]=7867;
	a[825]=7873;
	a[826]=7877;
	a[827]=7879;
	a[828]=7883;
	a[829]=7901;
	a[830]=7907;
	a[831]=7919;
	a[832]=7927;
	a[833]=7933;
	a[834]=7937;
	a[835]=7949;
	a[836]=7951;
	a[837]=7963;
	a[838]=7993;
	a[839]=8009;
	a[840]=8011;
	a[841]=8017;
	a[842]=8039;
	a[843]=8053;
	a[844]=8059;
	a[845]=8069;
	a[846]=8081;
	a[847]=8087;
	a[848]=8089;
	a[849]=8093;
	a[850]=8101;
	a[851]=8111;
	a[852]=8117;
	a[853]=8123;
	a[854]=8147;
	a[855]=8161;
	a[856]=8167;
	a[857]=8171;
	a[858]=8179;
	a[859]=8191;
	a[860]=8209;
	a[861]=8219;
	a[862]=8221;
	a[863]=8231;
	a[864]=8233;
	a[865]=8237;
	a[866]=8243;
	a[867]=8263;
	a[868]=8269;
	a[869]=8273;
	a[870]=8287;
	a[871]=8291;
	a[872]=8293;
	a[873]=8297;
	a[874]=8311;
	a[875]=8317;
	a[876]=8329;
	a[877]=8353;
	a[878]=8363;
	a[879]=8369;
	a[880]=8377;
	a[881]=8387;
	a[882]=8389;
	a[883]=8419;
	a[884]=8423;
	a[885]=8429;
	a[886]=8431;
	a[887]=8443;
	a[888]=8447;
	a[889]=8461;
	a[890]=8467;
	a[891]=8501;
	a[892]=8513;
	a[893]=8521;
	a[894]=8527;
	a[895]=8537;
	a[896]=8539;
	a[897]=8543;
	a[898]=8563;
	a[899]=8573;
	a[900]=8581;
	a[901]=8597;
	a[902]=8599;
	a[903]=8609;
	a[904]=8623;
	a[905]=8627;
	a[906]=8629;
	a[907]=8641;
	a[908]=8647;
	a[909]=8663;
	a[910]=8669;
	a[911]=8677;
	a[912]=8681;
	a[913]=8689;
	a[914]=8693;
	a[915]=8699;
	a[916]=8707;
	a[917]=8713;
	a[918]=8719;
	a[919]=8731;
	a[920]=8737;
	a[921]=8741;
	a[922]=8747;
	a[923]=8753;
	a[924]=8761;
	a[925]=8779;
	a[926]=8783;
	a[927]=8803;
	a[928]=8807;
	a[929]=8819;
	a[930]=8821;
	a[931]=8831;
	a[932]=8837;
	a[933]=8839;
	a[934]=8849;
	a[935]=8861;
	a[936]=8863;
	a[937]=8867;
	a[938]=8887;
	a[939]=8893;
	a[940]=8923;
	a[941]=8929;
	a[942]=8933;
	a[943]=8941;
	a[944]=8951;
	a[945]=8963;
	a[946]=8969;
	a[947]=8971;
	a[948]=8999;
	a[949]=9001;
	a[950]=9007;
	a[951]=9011;
	a[952]=9013;
	a[953]=9029;
	a[954]=9041;
	a[955]=9043;
	a[956]=9049;
	a[957]=9059;
	a[958]=9067;
	a[959]=9091;
	a[960]=9103;
	a[961]=9109;
	a[962]=9127;
	a[963]=9133;
	a[964]=9137;
	a[965]=9151;
	a[966]=9157;
	a[967]=9161;
	a[968]=9173;
	a[969]=9181;
	a[970]=9187;
	a[971]=9199;
	a[972]=9203;
	a[973]=9209;
	a[974]=9221;
	a[975]=9227;
	a[976]=9239;
	a[977]=9241;
	a[978]=9257;
	a[979]=9277;
	a[980]=9281;
	a[981]=9283;
	a[982]=9293;
	a[983]=9311;
	a[984]=9319;
	a[985]=9323;
	a[986]=9337;
	a[987]=9341;
	a[988]=9343;
	a[989]=9349;
	a[990]=9371;
	a[991]=9377;
	a[992]=9391;
	a[993]=9397;
	a[994]=9403;
	a[995]=9413;
	a[996]=9419;
	a[997]=9421;
	a[998]=9431;
	a[999]=9433;
	a[1000]=9437;
	a[1001]=9439;
	a[1002]=9461;
	a[1003]=9463;
	a[1004]=9467;
	a[1005]=9473;
	a[1006]=9479;
	a[1007]=9491;
	a[1008]=9497;
	a[1009]=9511;
	a[1010]=9521;
	a[1011]=9533;
	a[1012]=9539;
	a[1013]=9547;
	a[1014]=9551;
	a[1015]=9587;
	a[1016]=9601;
	a[1017]=9613;
	a[1018]=9619;
	a[1019]=9623;
	a[1020]=9629;
	a[1021]=9631;
	a[1022]=9643;
	a[1023]=9649;
	a[1024]=9661;
	a[1025]=9677;
	a[1026]=9679;
	a[1027]=9689;
	a[1028]=9697;
	a[1029]=9719;
	a[1030]=9721;
	a[1031]=9733;
	a[1032]=9739;
	a[1033]=9743;
	a[1034]=9749;
	a[1035]=9767;
	a[1036]=9769;
	a[1037]=9781;
	a[1038]=9787;
	a[1039]=9791;
	a[1040]=9803;
	a[1041]=9811;
	a[1042]=9817;
	a[1043]=9829;
	a[1044]=9833;
	a[1045]=9839;
	a[1046]=9851;
	a[1047]=9857;
	a[1048]=9859;
	a[1049]=9871;
	a[1050]=9883;
	a[1051]=9887;
	a[1052]=9901;
	a[1053]=9907;
	a[1054]=9923;
	a[1055]=9929;
	a[1056]=9931;
	a[1057]=9941;
	a[1058]=9949;
	a[1059]=9967;
	a[1060]=9973;
	int Test,temp,dis,wei1,wei2,wei3,wei4,i,k;
	cin>>Test;

	while(Test--)
	{
		while(q.size())q.pop();

		cin>>temp>>dis;

		q.push(temp);
		memset(ans,0,sizeof(ans));

		while(1)
		{
			temp=q.front();
			q.pop();
			if(temp==dis)
			{
				cout<<ans[temp]<<endl;
				break;
			}

			wei1=temp%10;
			wei2=(temp%100-wei1)/10;
			wei4=temp/1000;
			wei3=temp/100-wei4*10;

			for(i=1;i<=9;i=i+2)
			{
				k=wei4*1000+wei3*100+wei2*10+i;
				if(wei1!=i &&!ans[k]&& pend(k))
				{
					ans[k]=ans[temp]+1;
					q.push(k);
				}
			}
			for(i=0;i<=9;i++)
			{
				k=wei4*1000+wei3*100+i*10+wei1;
				if(wei2!=i &&!ans[k]&& pend(k))
				{
					ans[k]=ans[temp]+1;
					q.push(k);
				}
			}
			for(i=0;i<=9;i++)
			{
				k=wei4*1000+i*100+wei2*10+wei1;
				if(wei3!=i &&!ans[k]&& pend(k))
				{
					ans[k]=ans[temp]+1;
					q.push(k);
				}
			}
			for(i=1;i<=9;i++)
			{
				k=i*1000+wei3*100+wei2*10+wei1;
				if(wei4!=i &&!ans[k]&& pend(k))
				{
					ans[k]=ans[temp]+1;
					q.push(k);
				}
			}
		}
	}

	return 0;
}

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