using System;

public class Program

{

    public static void Main()

    {

        var result = Decrypt("dnotq");

        foreach(var r in result) {

            Console.WriteLine(r);   

        }

    }

    public static char[] Decrypt(string word) {

        // base check

        if (string.IsNullOrEmpty(word)) { 

            return null;

        }

        var result = new char[word.Length];

        var a = (int)'a';

        Console.WriteLine(a);

        // lets do the first word

        result[0] = (char)((int)word[0] - 1);

        for(int i = 1; i< word.Length; i++) {

            int temp = (int)word[i] - (int)word[i-1];

            while (temp <= a) {

                temp = temp + 26;

            }

            result[i] = (char)temp;

        }

        return result;

    }

}