Difference Between Primes

Problem Description

All you know Goldbach conjecture.That is to say, Every even integer greater than 2 can be expressed as the sum of two primes. Today, skywind present a new conjecture: every even integer can be expressed as the difference of two primes. To validate this conjecture, you are asked to write a program.

 

Input

The first line of input is a number nidentified the count of test cases(n<10^5). There is a even number xat the next nlines. The absolute value of xis not greater than 10^6.

 

Output

For each number xtested, outputstwo primes aand bat one line separatedwith one space where a-b=x. If more than one group can meet it, output the minimum group. If no primes can satisfy it, output 'FAIL'.

 

Sample Input

3

6

10

20

 

Sample Output

11 5

13 3

23 3

 

Source

2013 ACM/ICPC Asia Regional Online —— Warmup

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;

const int N= ;
int prime[],cnt;
bool isprime[N];

void Prime()
{
    cnt =;
    memset(isprime,true,sizeof(isprime));
    isprime[]=false;
    for(int i=; i<N; i++)
        if(isprime[i])
        {
            for(int j=i+i; j<N; j+=i) isprime[j] = false;
            prime[cnt++] = i;
        }
}

void finder(int m)
{
    for(int i=; i<cnt; i++)
    {
        if(prime[i]>m && isprime[prime[i]-m])
        {
            printf("%d %d\n",prime[i],prime[i]-m);
            return ;
        }
    }
    puts("FAIL");
}
int main()
{
    int t,m;
    Prime();
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&m);
        finder(m);
    }

    return ;
}