func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int a, b;     cin >> a >> b;     if (b == 1 && a == 9) {       cout <<  9 10  << endl;     } else if (b - a == 1) {       cout << a <<     << b << endl;     } else if (a == b) {       cout << a <<  1   << b <<  2  << endl;     } else {       cout <<  -1  << endl;     }   }   