using System;

public class Hello
{
    static void Main()
    {
        var s0 = "abcdefghijklmnopqrstuvwxyz";
        var s = Console.ReadLine().Trim();
        getAns(s0, s);
    }
    static void getAns(string s0, string s)
    {
        for (int i = 0; i < 26; i++)
            if (s0[i] != s[i]) { Console.WriteLine("{0}to{1}", s0[i], s[i]); break; }
    }
}