func_code_string: #include <bits/stdc++.h>   using namespace std;   long long modulo(long long base, long long exp, long long m);   int main() {     int x;     cin >> x;     if (x <= 1)       cout <<  -1 ;     else {       cout << x <<     << x;     }     return 0;   }   long long modulo(long long base, long long exp, long long m) {     long long answer = 1;     while (exp > 0) {       if (exp % 2 == 1) answer = (answer * base) % m;       exp = exp / 2;       base = (base * base) % m;     }     return answer;   }   