using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        List<string> result = wave("hello");

        foreach(var item in result)

            Console.WriteLine(item);

    }

​

    public static List<string> wave(string str)

    {

        str = str.ToLower();

        int length = str.Length;

        List<string> result = new List<string>(length);

        for(int i=0; i<length; i++){

            string word = "";

            for(int j=0; j<length; j++){

                if(i != j)

                    word += str[j].ToString();

                else

                    word += str[i].ToString().ToUpper();

            }

            if(word != str)

                result.Add(word);

        }

        return result;

    }

}