using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public class Test
{
	public static void Main()
	{
		    List<string> _ids = new List<string>() { "aaa", "bbb", "ccc", "ddd" };
            var first = _ids.First();
            var last = _ids.Last();
            Console.WriteLine(first);
            Console.WriteLine(last);
	}
}