let rec remove((l, occ, elem):int list * int * int) =
  if occ=0 then (l,occ) else
    match l with
    |[]->([],occ)
    |[x]->if x=elem then ([],(occ-1)) else ([x],occ)
    |x::xs->
      let (p,_)=remove(xs,occ,elem)
      in
      if x=elem then remove(xs,(occ-1),elem) else (x::p,occ)
System.Console.WriteLine(remove(([10;2;3], 2, 2)))