using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}

​

public class Vector

{

    public double X { get; set; }

    public double Y { get; set; }

    public Vector(double x, double y)

    {

        X = x;

        Y = y;

    }

    // Make an indexer

    public double this[int index] 

    {

        get

        {

            if (index == 0) { return X; }

            else if(index == 1) { return Y;}

            else { throw new IndexOutOfRangeException(); }

        }

        set 

        {

            if (index == 0) { X = value; }

            else if (index == 1) { Y = value; }

            else { throw new IndexOutOfRangeException(); }

        }

    }

    // overloading operator +

    public static Vector operator +(Vector v1, Vector v2)

    {

        return new Vector(v1.X + v2.X, v1.Y + v2.Y);

    }

    // multiple overloads the same operator

    public static Vector operator +(Vector v, double scalar)

    {

        return new Vector(v.X + scalar, v.Y + scalar);

    }

    // overloading unary operator -

    public static Vector operator -(Vector v)

    {

        return new Vector(-v.X, -v.Y);

    }

    // overloading relational operators - return type must be bool, and in pairs!

    public static bool operator ==(Vector v1, Vector v2)

    {

        return ((v1.X == v2.X) && (v1.Y == v2.Y));

    }

    public static bool operator !=(Vector v1, Vector v2)

    {

        return !(v1 == v2);

    }

}