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 Go (1.6) (judge verdict: Time Limit Exceeded)

package main

import (
	"fmt"
)

func main() {
	var N, M int
	fmt.Scan(&N, &M)
	// X := make([]int, M)
	// Y := make([]int, M)
	// Z := make([]int, M)
	a := make([]int, N)
	b := make([][]int, N)
	for i := 0; i < N; i++ {
		a[i] = i
		b[i] = []int{i}
	}
	for i := 0; i < M; i++ {
		var X, Y, Z int
		fmt.Scan(&X, &Y, &Z)
		X--
		Y--
		ax := a[X]
		ay := a[Y]
		if len(b[ay]) < len(b[ax]) {
			for _, bb := range b[ay] {
				a[bb] = a[X]
				b[a[X]] = append(b[a[X]], bb)
			}
		} else {
			for _, aa := range b[ax] {
				a[aa] = a[Y]
				b[a[Y]] = append(b[a[Y]], aa)
			}
		}
	}

	// count
	m := map[int]int{}
	for _, ax := range a {
		m[ax] = 1
	}

	fmt.Printf("%v\n", len(m))
}