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 Scala (2.11.7) (judge verdict: Wrong Answer)

import java.util.Scanner

object Main {
  def main(args: Array[String]): Unit = {
    val sc = new Scanner(System.in)
    val n, m = sc.nextInt()

    val par = new Array[Int](n)
    init(par)

    for (i <- 0 until m) {
      val x, y, z = sc.nextInt()
      unite(par, x-1, y-1)
    }

    var ans = 0

    for (i <- par.indices) {
      if (isParent(par, i)) ans += 1
    }

    println(ans)
  }

  def isParent(par: Array[Int], x: Int): Boolean = {
    par(x) == x
  }

  def init(par: Array[Int]): Unit = {
    for (i <- par.indices) {
      par(i) = i
    }
  }


  @scala.annotation.tailrec
  def root(par: Array[Int], x: Int): Int = {
    if (par(x) == x) {
      x
    } else {
      par(x) = x
      root(par, par(x))
    }
  }

  def same(par: Array[Int], x: Int, y: Int): Boolean = {
    root(par, x) == root(par, y)
  }

  def unite(par: Array[Int], x: Int, y: Int): Unit = {
    if (!(root(par, x) == root(par, y)))
      par(root(par, x)) = root(par, y)
  }
}