POJ 2591

 #include<iostream>
 #include<stdio.h>
 #define MAXN  10000001
 using namespace std;

 int a[MAXN];
 void give_set();
 int min(int i,int j);
 int main()
 {
     //freopen("acm.acm","r",stdin);
     give_set();
     int num;
     while(cin>>num)
     {
         cout<<a[num-]<<endl;
     }
 }

 void give_set()
 {
     a[] = ;
     int m;
     int len = ;
     int x;
     int y;
     x = ;
     y = ;
     while(len < MAXN)
     {
         m = min(*a[x]+,*a[y]+);
         if(m == *a[x]+)
             ++ x;
         if(m == *a[y]+)
             ++ y;
         a[len++] = m;
     }
 }
 int min(int a,int b)
 {
     return a < b ? a : b;
 }