static void Main(string[] args)
{
ImmutableList <int> list = ImmutableList.Create <int>();
IImmutableList <int> list2 = list.Cons(5);
int headvalue = list2.Head();
int tailvalue = list2.Tail();
IImmutableList <int> list3 = list2.Drop(2);
IImmutableList <int> list4 = list3.Reverse();
}