#include <cstdio>
#include <cmath>
#include <memory>
const int MAX = 170001;
bool prime[MAX];
int p[15001];
void findPrime()
{
     int i,j;
     memset(prime,true,sizeof(prime));
     //for(i = 0;i <MAX; i++)
       //    prime[i] = true;
     for(i = 2;i < sqrt(MAX);)
     {
           if(prime[i] == true)
                 for(j = i * i;j < MAX; j += i)
                       prime[j] = false;
           if(i == 2)
              i++;
           else
              i += 2;
     }
}
int main()
{
    findPrime();
    int i,k,j;
    j = 1;
    for(i = 2;i < MAX; i++)
    {
          if(prime[i])
                      p[j++] = i;
    }
    scanf("%d",&k);
    while(k--)
    {
              scanf("%d",&i);
              printf("%d\n",p[i]);
    }
    return 0;
}

I got it.
In the FAQ,it says that,
In C/C++ you cannot call functions from header math.h with integer parameters. This code will not be compiled: sqrt(2). You can write correctly sqrt((double)2) or sqrt(2.0).