using System.Collections;
using System.Collections.Generic;
public static void Main()
List<int> lefts = Enumerable.Range(1, 10).ToList();
List<int> rights = Enumerable.Range(5, 15).ToList();
join r in rights on l equals r into collect
from res in collect.DefaultIfEmpty()
System.Console.WriteLine(q);
System.Console.WriteLine(a.X.ToString() +": "+ a.Y.ToString());