POJ3641 Pseudoprime numbers

Fermat's theorem states that for any prime number p and for any integer a > 1, ap = a (mod p). That is, if we raise a to the pth power and divide by p, the remainder is a. Some (but not very many) non-prime values of p, known as base-a pseudoprimes, have this property for some a. (And some, known as Carmichael Numbers, are base-apseudoprimes for all a.)

Given 2 < p ≤ 1000000000 and 1 < a < p, determine whether or not p is a base-apseudoprime.

Input

Input contains several test cases followed by a line containing "0 0". Each test case consists of a line containing p and a.

Output

For each test case, output "yes" if p is a base-a pseudoprime; otherwise output "no".

Sample Input

3 2
10 3
341 2
341 3
1105 2
1105 3
0 0

Sample Output

no
no
yes
no
yes
yes

#include<stdio.h>  
#include<math.h> 
typedef long long ll;
int isprime(int n) {
	if(n == 1) return 0;
	for(int i = 2; i * i <= n; ++i) {
		if(n % i == 0) return 0;
	}
	return 1;
}
ll pow_mod(ll a, ll n, ll MOD) {
	ll res = 1;
	while (n) {
		if(n&1) res = res * a % MOD;
		a = a * a % MOD;
		n >>= 1;
	}
	return res ;
}
int main()  
{   
    long long a,p;
    while(scanf("%lld %lld",&p,&a)&&a||p)  
    {
    	if(isprime(p))
    	printf("no\n");
    	else
    	{
    		if(pow_mod(a,p,p)==a)
    		printf("yes\n");
    		else
    		printf("no\n");
		}
	}
    return 0;  
}