Book writing

#include <bits/stdc++.h>

using namespace std;

typedef unsigned long long int ull;

ull modpow(ull a, ull p, ull m) {
    if (p == 0) return 1;
    if (p%2 == 0) {
        a = modpow(a, p/2, m);
        return (a*a)%m;
    }
    return (a*modpow(a, p-1, m))%m;
}

int main() {
    ull n, m;
    cin >> n >> m;
    
    if (m == 1)
        cout << "0" << endl;
    else
        cout << modpow(3, n-1, m) << endl;
    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

Test 15

Verdict: ACCEPTED