a^b（快速幂模版）

#include <iostream>

using namespace std;

int main() {
    
    int a, b , p;
    cin >> a >> b >> p;
    int res = 1 % p;
    
    while(b) {
        if(b&1) res = res * 1ll * a % p;
        a = a * 1ll * a % p;
        b >>= 1;
    }
    cout << res << endl;
    
    return 0;
}

import java.util.*;
class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long a = sc.nextLong();
        long b = sc.nextLong();
        long p = sc.nextLong();
        long res = 1 % p;
        while(b != 0) {
            if((b&1) != 0) res = res * a % p;
            a = a * a % p;
            b >>= 1;
        }
        
        System.out.print(res%p);
        
    } 
}