快速幂求模

#include<iostream>
#include<cstdio>
using namespace std;
typedef long long LL;
int main()
{
    LL b,p,k;
    cin>>b>>p>>k;
    LL ans=1;
    LL x=p;
    LL y=b;
    while(p>0)
    {
        if(p&1)
        {
            ans=ans*b%k;
            }    
        b=b*b%k;
        p=p>>1;
    }
    cout<<y<<"^"<<x<<" mod "<<k<<"="<<ans%k;
    return 0;
}