Pseudoprime numbers

判断伪素数

#include <stdio.h>
#include <math.h>

int quick_mod (int a, int b, int mod)
{
  int ans = 1;
  a = a % mod;
  while(b>0) {
    if(b % 2 == 1) 
    ans = (ans * a) % mod;
    b = b/2;
    a = (a * a) % mod;
  }
  return ans;
}

int isprime (long long p)
{
    long long i;
    for(i=2;i<=sqrt(p);i++)
        if(p % i == 0)
        return 0;
    return 1;
}

int main(int argc, char *argv[])
{
    long long a,p;
    while(scanf("%lld%lld",&p,&a)!=EOF  && (a!=0 || p!=0))
    {
        if (isprime(p))
            printf("no\n");
        else
        {
            if(quick_mod(a,p,p) == a)
            printf("yes\n");
            else
            printf("no\n");
        }
    }
    return 0;
}