Inverse modulo in C++ (a^-1 % m (m is prime)) (fermat's little theorem)

invMod.cpp

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

ll powMod(ll a, ll b, ll m) {
    ll res = 1;
    while (b) {
        if (b % 2) res = (res * a) % m;
        a = (a * a) % m;
        b /= 2;
    }
    return res;
}

ll invMod(ll x, ll m) {  // x^-1 % m (m is prime)
    return powMod(x, m - 2, m);
}

int main() {
    ll MOD = 998244353;
    cout << (2 * invMod(3, MOD)) % MOD; // 665496236
}