func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MOD = 1e9 + 7;   int calc(long long a, long long n) {     long long res = 1;     while (n > 0) {       if (n & 1) res = (res * a) % MOD;       a = (a * a) % MOD;       n /= 2;     }     return res;   }   int main() {     ios_base::sync_with_stdio(0);     long long n;     cin >> n;     long long x = calc(2, n);     cout << x * (x + 1) / 2 % MOD;     return 0;   }   