func_code_string: #include <bits/stdc++.h>   using namespace std;   long long n, mod;   long long expsq(long long base, long long exp) {     if (exp == 0) return 1ll;     if (exp == 1) return base;     if (exp & 1)       return (base * expsq((base % mod * base % mod) % mod, (exp - 1) / 2)) % mod;     return expsq((base % mod * base % mod) % mod, exp / 2) % mod;   }   int main() {     cin >> n >> mod;     long long ans = expsq(3ll, n);     ans--;     while (ans < 0) ans += mod;     cout << ans % mod;   }   