using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var l = new List<double>() { 0, 0 + 1e-7, 0 + 2e-7, 1 - 1e-7, 1 };

        var result = new Dictionary<double,List<double>>();

        foreach(var i in l)

        {

            double? key = result.Keys.Any(x => IsWithinTolerance(x,i)) ? result.Keys.First(x => IsWithinTolerance(x,i)) : default(double?);

            if(key == null)

            {

                result.Add(i, new List<double> { i });

            }

            else

            {

                result[key.Value].Add(i);

            }

        }

        Console.WriteLine(string.Join("\n", result.Select(x => string.Join(" ", x.Value))));

    }

    static bool IsWithinTolerance(double x, double y)

    {

        return Math.Abs(x - y) < 1e-6;

    }

}