func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     if (n == 1) {       cout << 0 << endl;       return 0;     }     if (n == 2) {       cout << 3 << endl;       return 0;     }     long long a, b, c;     a = 0;     b = 3;     c = 6;     for (int i = 3; i <= n; i++) {       c = ((a * 3) % 1000000007 + (b * 2) % 1000000007) % 1000000007;       a = b;       b = c;     }     cout << c << endl;     return 0;   }   