let rec removeNode e = function
     | Lf               -> Lf
     | Br (v, t1, t2)   -> if (funcID (<) (e,v)) then (Br(v, removeNode e t1, t2))
                           elif (funcID (>) (e,v)) then (Br(v, t1, removeNode e t2))
                           else match (t1, t2) with
                                 | (Lf, Lf)                                -> Lf
                                 | (Br(v1, t11, t21), Lf)                  -> Br (v1, t11, t21)
                                 | (Lf, Br(v2, t12, t22))                  -> Br (v2, t12, t22)
                                 | (Br(v1, t11, t21), Br(v2, t12, t22))    -> let (min, newTree) = removeMinNode (Br(v2, t12, t22))
                                                                              Br (min, Br(v1, t11, t21), newTree)