using System;

using System.Linq;

using System.Collections.Generic;

​

namespace IncrementCheck

{

    public class MainClass

    {

        public static void Main (string[] args)

        {

            StrokeCollection strokeCollection = new StrokeCollection ();

            strokeCollection.Add (new Stroke (){ 

                    new Point{ x = 2, y = 3 }, 

                    new Point{ x = 21, y = 5 }, 

                    new Point{ x = 7, y = 23 },

                    new Point{ x = -34, y= 22}

            });

            var res = (from stroke in strokeCollection

                      from point in stroke

                      group point by 1 into g

                      select new { Left = g.Min (p => p.x), Right = g.Max (p => p.x)}).FirstOrDefault ();

            Console.Write (res.Left + " ------ " + res.Right);

        }

    }

​

    public class StrokeCollection: List<Stroke>

    {

    }

​

    public class Stroke : List<Point>

    {

    }

​

    public class Point

    {

        public int x;

        public int y;

    }

}

​