structure Bag =
struct
datatype 'a tree = Leaf | Node of 'a * int * 'a tree * 'a tree

val empty = Leaf

fun size Leaf = 0
  | size (Node (k, v, left, right)) = 1 + size left + size right

fun add Leaf newKey = Node (newKey, 1, Leaf, Leaf)
  | add (Node (nodeKey, nodeValue, left, right)) newKey =
    if nodeKey = newKey then (Node (nodeKey, nodeValue + 1, left, right))
    else if nodeKey < newKey then Node (nodeKey, nodeValue, left, add right newKey)
    else Node (nodeKey, nodeValue, add left newKey, right)

fun values Leaf = []
  | values (Node (_, v, left, right)) = [v] @ values left @ values right

end


fun readInt () =
    valOf (TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn)


fun makeBag l =
    List.foldl (fn (a, acc) =>
                   Bag.add acc a)
               Bag.empty
               l

val () =
    let
        val n = readInt ()
        val a_s = List.tabulate (n, fn _ => readInt ())

        val bag = makeBag a_s
        val ans = List.length (List.filter (fn v => v = 1) (Bag.values bag))
    in
        print (Int.toString ans ^ "\n")
    end