#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <map>
using namespace std;
typedef long long ll;
#define rep(i,n) for (int i = 0; i < int(n);i++)

int main(){
   string s;
   cin >> s;
   char c = 'a';
   string ans = "";
   rep(i,26){
     if (s[i] != c) {
       ans += c;
       ans += "to";
       ans += s[i];
       break;
     }
     c++;
   }
   cout << ans << endl;
   


   return 0;
   

}