Finding inverse

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>
#include <queue>
#include <climits>
//#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll extgcd(ll a, ll b, ll &x, ll &y) {
    if (b == 0) {
        x = 1;
        y = 0;
        return a;
    }
    ll x1, y1;
    ll g = extgcd(b, a % b, x1, y1);
    x = y1;
    y = x1 - (a / b) * y1;
    return g;
}

ll modInverse(ll a, ll m) {
    ll x, y;
    ll g = extgcd(a, m, x, y);
    
    if (g != 1) {
        return -1;
    }
    
    x = (x % m + m) % m;
    if (x == 0) x = m;
    
    return x;
}

ll modpow(ll x, ll n, ll m) {
    if (n == 0) return 1%m;
    ll u = modpow(x,n/2,m);
    u = (u*u)%m;
    if (n%2 == 1) u = (u*x)%m;
    return u;
}

void task1(){
    ll n;
    cin >> n;

    for(ll i = 0; i < n; i++){
        ll a, b;
        cin >> a >> b;
        cout << modpow(a, b, 1000000007) << endl;
    }

    
}

void task2(){
    ll a, M;
    cin >> a >> M;
    
    cout << modInverse(a, M) << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    task2();
    
    return 0;

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED