using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var _recentlyUsedItems = new List<int> { };

        var indexToRemove = _recentlyUsedItems.IndexOf(3);

        if (indexToRemove >= 0)

        {

            _recentlyUsedItems.RemoveAt(indexToRemove);

        }

        Console.WriteLine(string.Join(", ", _recentlyUsedItems));

    }

}