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: Accepted)

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"strconv"
)

var sc *bufio.Scanner

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func ufRoot(e []int, x int) int {
	for {
		if e[x] == x {
			return x
		}
		x = e[x]
	}
}

func ufUnite(e []int, x int, y int) {
	rx := ufRoot(e, x)
	ry := ufRoot(e, y)
	if rx != ry {
		e[rx] = ry
		e[x] = ry
	}
}

func answer(reader io.Reader, writer io.Writer) {
	sc = bufio.NewScanner(reader)
	sc.Split(bufio.ScanWords)

	n := nextInt()
	m := nextInt()
	t := make([]int, n)
	for i := 0; i < n; i++ {
		t[i] = i
	}

	for i := 0; i < m; i++ {
		x := nextInt()
		y := nextInt()
		_ = nextInt()
		x--
		y--
		ufUnite(t, x, y)
	}
	//fmt.Printf("%v\n", t)
	count := 0
	for i := 0; i < n; i++ {
		if t[i] == i {
			count++
		}
	}
	_, _ = fmt.Fprintf(writer, "%d", count)
}

func main() {
	answer(os.Stdin, os.Stdout)
}