using System.Numerics;

public class Program
{
    public static void Main()
    {
        //int num = int.Parse(Console.ReadLine() ?? string.Empty);
        //string[] str = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        string str = Console.ReadLine() ?? string.Empty;

        string alph = "abcdefghijklmnopqrstuvwxyz";

        char a = 'a';
        char b = 'b';

        for (int i = 0;i < alph.Length;i++)
        {
            if(str[i]!= alph[i])
            {
                a = str[i];
                b = alph[i];
                break;
            }
        }
        Console.WriteLine("{0}to{1}",b,a);
    }
}