POJ 3641 快速幂+素数

#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
typedef long long ll;
bool judge_prime(ll k)
{
ll i;
ll u=int(sqrt(k*1.0));
for(i=2;i<=u;i++)
{
if(k%i==0)
return 0;
}
return 1;
}
ll mod_pow(ll x,ll n,ll mod)
{
ll res=1;
while(n>0)
{
if(n&1) res=res*x%mod;
x=x*x%mod;
n>>=1;
}
return res;
}
int main()
{
ll num=0,a,p;
while(~scanf("%lld %lld",&p,&a))
{
if(p==0&&a==0) {num=0;}
else{
if(judge_prime(p)) cout<<"no"<<endl;
else{
num=mod_pow(a,p,p);
if(num==a) cout<<"yes"<<endl;
else cout<<"no"<<endl;}}
}
return 0;
}