using System;

using System.Linq;

using System.Diagnostics;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        const int count = 25000;

        var collection = Enumerable.Range(1, count);

        var stopwatch = new Stopwatch();

        stopwatch.Start();

        for (int i = 0; i < count; i++) {

            var x = collection.FirstOrDefault(y => y == i);

        }

        stopwatch.Stop();

        Console.WriteLine("List time: " + stopwatch.Elapsed);

        stopwatch.Reset();

        stopwatch.Start();

        var dictionary = collection.ToDictionary(v => v);

        for (int i = 0; i < count; i++) {

            var x = dictionary.ContainsKey(i);

        }

        stopwatch.Stop();

        Console.WriteLine("Dictionary time: " + stopwatch.Elapsed);

    }

}