using System;

​

namespace Test

{

    class Program

    {

        static char f(string s)

        {

            int i=0,j=0;for(;i<s.Length;)j+=s[i++]-97;return(char)(97+j%26);

        }

        static void Main()

        {

            Console.WriteLine(f("helloworld"));    // k

            Console.WriteLine(f("abcdef"));        // p

            Console.WriteLine(f("codegolf"));      // h

            Console.WriteLine(f("stackexchange")); // e

            Console.WriteLine(f("aaaaa"));         // a

        }

    }

}