func_code_string: #include <bits/stdc++.h>   using namespace std;   long long n, A, B, C = 1;   const long long E = 1e9 + 7;   int main() {     cin >> n;     if (n <= 1) {       cout << 0 << endl;       return 0;     }     for (long long i = 2; i < n; i++) {       A = B;       B = C;       C = 2 * B + 3 * A;       C %= E;     }     long long ans = (3 * C) % E;     cout << ans << endl;     return 0;   }   