using System;
using System.Collections.Generic;

public class Test
{
	public static void Main() {
		var list = new List<Point>();
		list.Add(new Point(10, 20));
		list.Add(new Point(20, 40));
		list.Add(new Point(40, 80));
		
		list[1].X = 30;
		
		foreach(var pt in list) {
			Console.WriteLine(pt);
		}
	}
	
	class Point {
		
		public int X { get; set; }
		public int Y { get; set; }
		
		public Point(int x, int y) {
			X = x;
			Y = y;
		}
		
		public override String ToString() {
			return String.Format("X = {0}, Y = {1}", X, Y);
		}
	}
}