func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     if (n % 2 == 1) {       cout << -1 << endl;     } else {       cout <<  2 1 ;       for (int i = 3; i < n; i += 2) {         cout <<     << i + 1 <<     << i;       }       cout << endl;     }     return 0;   }   