题解在此

#include <iostream>
using namespace std;
int main(){
    long long b,p,k;
    cin>>b>>p>>k;
    cout<<b<<'^'<<p<<" mod "<<k<<'=';
    long long sum=1;
    while (p){
        if (p%2==1){
            sum=sum*b%k;
        }
        b=b*b%k;
        p/=2;
    }
    cout<<sum;
    return 0;
}