using System;

public class Program

{

    public static void Main()

    {

        var b = new B(1, 2);

        var c = new C(3, 4);

        Console.WriteLine(b.x +" : "+c.x);

    }

    public class A 

    {

        public int x;

        public A(int x)

        {

            this.x = x;

        }

    }

    public class B : A

    {

        private int y;

        public B(int x, int y) : base(x)

        {

            this.y = y;

        }

    }

    public class C : A

    {

        private int z;

        public C(int x, int z) : base(x)

        {

            this.z = z;

        }

    }

}