Problem:
Score : 500 points

Problem Statement

There are N cards placed face down in a row. On each card, an integer 1 or 2 is written.

Let A_i be the integer written on the i-th card.

Your objective is to guess A_1, A_2, ..., A_N correctly.

You know the following facts:

For each i = 1, 2, ..., M, the value A_{X_i} + A_{Y_i} + Z_i is an even number.

You are a magician and can use the following magic any number of times:

Magic: Choose one card and know the integer A_i written on it. The cost of using this magic is 1.

What is the minimum cost required to determine all of A_1, A_2, ..., A_N?

It is guaranteed that there is no contradiction in given input.

Constraints

All values in input are integers.

2 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq X_i < Y_i \leq N

1 \leq Z_i \leq 100

The pairs (X_i, Y_i) are distinct.

There is no contradiction in input. (That is, there exist integers A_1, A_2, ..., A_N that satisfy the conditions.)

Input

Input is given from Standard Input in the following format:

N M
X_1 Y_1 Z_1
X_2 Y_2 Z_2
\vdots
X_M Y_M Z_M

Output

Print the minimum total cost required to determine all of A_1, A_2, ..., A_N.

Sample Input 1

3 1
1 2 1

Sample Output 1

2

You can determine all of A_1, A_2, A_3 by using the magic for the first and third cards.

Sample Input 2

6 5
1 2 1
2 3 2
1 3 3
4 5 4
5 6 5

Sample Output 2

2

Sample Input 3

100000 1
1 100000 100

Sample Output 3

99999

Solution in OCaml (4.02.3) (judge verdict: Accepted)

let rec find x uf =
  if uf.(x) < 0 then
    x
  else
    let x' = find uf.(x) uf in
    uf.(x) <- x';
    x'

let unite x y uf =
  let x, y = find x uf, find y uf in
  if x <> y then
    if uf.(x) < uf.(y) then begin
      uf.(x) <- uf.(x) + uf.(y);
      uf.(y) <- x
    end else begin
      uf.(y) <- uf.(x) + uf.(y);
      uf.(x) <- y
    end

module S = Set.Make(struct type t = int let compare = (-) end)
  
let () =
  Scanf.scanf "%d %d" @@ fun n m ->
  let uf = Array.make n (-1) in
  for i = 1 to m do Scanf.scanf " %d %d %d" @@ fun x y _ -> unite (x-1) (y-1) uf done;
  Array.init n (fun i -> find i uf)
  |> Array.fold_left (fun s x -> S.add x s) S.empty
  |> S.cardinal |> Printf.printf "%d\n"