using System;

public class Program

{

    public static void Main()

    {

        Program P = new Program();

        Console.WriteLine(string.Join(",", P.reverseString(["H","a","n","n","a","h"])));

    }

    public string[] reverseString(string[] s) {

        int i = 0, j = s.Length-1;

        while (i<j) {

            var x = s[i];

            var y = s[j];

            s[i] = y;

            s[j] = x;

            i++;

            j--;

        }

        return s;

    }

}