#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  string alpha = "abcdefghijklmnopqrstuvwxyz";
  string s;
  cin >> s;
  for (int i = 0; i < (int)s.length(); i++) {
    if (s[i] != alpha[i]) {
      cout << alpha[i] << "to" << s[i] << '\n';
      break;
    }
  }
  return 0;
}