using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        //for the given array of points the result should be 2

        var result = new Ray().solution(new Point2D[] {

            new Point2D { x = -1, y = -2 },

            new Point2D { x = 1, y = 2 },

            new Point2D { x = 2, y = 4 },

        });

        Console.WriteLine(result);

    }

}

​

public class Ray

{

    //do not change the method signature

    public int solution(Point2D[] arr)

    {

            HashSet<Point2D> toSkip = new HashSet<Point2D>();

            int resultedCountOfRays = 0;

            for (var i = 0; i < arr.Length; i++)

            {

                if (arr[i].x == 0 && arr[i].y == 0)

                {

                    continue;

                }

                if (!toSkip.Contains(arr[i]))

                {

                    var currentItem = arr[i];

                    resultedCountOfRays++;

                    for (var j = i+1; j < arr.Length; j++)

                    {

                        if (i != j)

                        {

                            var potentialItem = arr[j];

​

                            if (IsInFXRange(currentItem.x, currentItem.y, potentialItem.x, potentialItem.y))

                            {

                                toSkip.Add(potentialItem);

                            }

                        }

                    }

                }

            }

​

            return resultedCountOfRays;

    }

         private bool IsInFXRange(long vx1, long vy1, long xx, long yy)

        {

            long x1 =  vx1;

            long y1 =  vy1;

            // ray goes from vector's coords to (0,0); 

            long x2 = 0;

            long y2 = 0;

            long x = xx;

            long y = yy;

             // formula got from algebra 8 grade.

            return ((y1 - y2) * x) + ((x2 - x1) * y) + (x1 * y2 - x2 * y1) == 0;

        }

}

​

public class Point2D

{

    public long x;

    public long y;

}

​