python/TangDou/AcWing_TiGao/T6/WeiYunSuan/90_1.cpp

#include <bits/stdc++.h>
using namespace std;

typedef long long LL;
LL a, b, p, res;

int main() {
    cin >> a >> b >> p;

    // 龟速乘
    while (b) {
        if (b & 1) res = (res + a) % p;
        a = (a + a) % p;
        b >>= 1;
    }

    cout << res << endl;
    return 0;
}