using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var maList = new List<int>(){ 1, 1, 2, 3};

        var first  = maList.FirstOrDefault(x => x == 1);

        var single = maList.SingleOrDefault(x => x == 1);

        Console.ReadLine();

    }

}