using System;

public class Program

{

    public static void Main()

    {

        int[] num = new int[4];

        string numbers = "";

        for(int i = 0; i < 4; i++) {

            do {

                Console.Clear();

                Console.WriteLine("Write four numbers");

                Console.Write(numbers);

                string answer = Console.ReadLine();

                int.TryParse(answer, out num[i]);

                if(answer == "0") { 

                    break; 

                }

            } while(num[i] == 0);

            numbers += num[i] + ", ";

        }

        int max = num[0];

        for(int i = 1; i < 4; i++) {

            if(max < num[i]){

                max = num[i];

            }

        }

        Console.WriteLine("\nHighest number is {0}", max);

    }

}