func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1e5 + 5;   const int MOD = 1000000007;   void solve() {     int n;     cin >> n;     vector<vector<int>> dp(4, vector<int>(n + 1, 0));     dp[3][0] = 1;     for (int i = 1; i < n + 1; i++)       for (int j = 0; j < 4; j++)         for (int k = 0; k < 4; k++)           if (k != j) dp[j][i] = (dp[j][i] + dp[k][i - 1]) % MOD;     cout << dp[3][n] <<   n ;   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     int t = 1;     while (t--) {       solve();     }     return 0;   }   