using System;

public class Program

{

    public static void Main()

    {

        var stringToReverse = "abc123";

        Console.WriteLine(Reverse(stringToReverse));

    }

    public static string Reverse(string stringToReverse)

    {

        // base case returns single character

        if (stringToReverse.Length == 1)

        {

            return stringToReverse;

        }

        // return the last character in the string followed by the reverse of remaining part of string

        return stringToReverse[stringToReverse.Length - 1] + Reverse(stringToReverse.Substring(0,(stringToReverse.Length-1)));

    }

}