What is the problem with my code?

#include <iostream>
using namespace std;
#include <cmath>

bool check_prime(double n) {
    int c;
    for (c=2;c<= sqrt(n);c++) {
        if((int) n%c==0)
            return 0;
    }
    if(c==(int) n)
        return 1;
}

int nth_prime(int n){
    int m=1;
    while (n>0) {
        m++;
        if (m == 2) {
            n--;
        }
        if (m%2!=0) {
            if (check_prime(m)==1) {
                n--;
            }
        }
    }
    return m;

}

int main()
{
    int n,m,i,a[15000],s;
    scanf("%d",&n);
    for(i=0;i<n;i++){
        scanf("%d",&a[i]);
    }
    for(i=0;i<n;i++){
        s = nth_prime(a[i]);
        printf("%d\n",s);
    }
    return 0;
}

Read about Sieve of Eratosthenes from this link :

 http://lightoj.com/article_show.php?article=1001