func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     if (n < 6)       cout << -1 << endl;     else {       for (int i = 2; i <= 4; i++) cout << 1 <<     << i << endl;       for (int i = 5; i <= n; i++) {         cout << 2 <<     << i << endl;       }     }     for (int i = 1; i < n; i++) {       cout << i <<     << i + 1 << endl;     }   }   