using System;

public class Program

{

    public static void Main()

    {

        int x,y,z;

        Console.WriteLine("Please write a number.");

        x = int.Parse(Console.ReadLine());

        Console.WriteLine("Please write another number.");

        y = int.Parse(Console.ReadLine());

        Console.WriteLine("Please write another number.");

        z = int.Parse(Console.ReadLine());

        if ( x == y || x == z || y == z)

        {

            Console.WriteLine("The numbers must be different, please start again.");

        }

        else if (y > x && x > z)     // y x z

        {

            Console.WriteLine("The middle number is: " +x);

        }

        else if (z > x && x > y)    // z x y

        {

            Console.WriteLine("The middle number is: " +x);

        }

        else if ( x > y && y > z) // x y z

        {

            Console.WriteLine("The middle number is: " +y);

        }

        else if ( z > y && y > x) // z y x

        {

            Console.WriteLine("The middle number is: " +y);

        }

        else if (x > z && z > y) // x z y 

        {

            Console.WriteLine("The middle number is: " +z);

        }

        else if (y > z && z > x) // y z x

        {

            Console.WriteLine("The middle number is: " +z);

        }

    }

}

​