using System;

public class Program

{

    public static void Main()

    {

        double x,a,b,c,d,e;

        Console.Write("x=");

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

        a=x/1000;

        b=x/100%10;

        c=x/10%10;

        d=x%10;

        e=a+d;

        if (a+d==b+c)

        {

            Console.Write("да {0}", e);

        }

                else

                    Console.Write("не");

    }

}

​

​