Function powmod

test/test_discrete_log.cpp:9–19

int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }

int powmod(int a, int b, int m) {
    int res = 1;
    while (b > 0) {
        if (b & 1) {
            res = (res * 1ll * a) % m;
        }
        a = (a * 1ll * a) % m;
        b >>= 1;
    }
    return res;
}

namespace DiscreteLog {
#include "discrete_log.h"