#include <iostream>
#include <string> 
using namespace std;

int main(){
    string s, t; cin >> t;
    s = "abcdefghijklmnopqrstuvwxyz";
    for(int i = 0; i < s.size(); i++){
        if(s[i] != t[i]){
            cout << (char)('a' + i) << "to" << t[i] << endl;
            break;
        }
    }
}