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 (
    "fmt"
)

var mp map[int]map[int]bool
var chk map[int]bool

func main() {
    var n, m int
    fmt.Scan(&n, &m)

    mp = make(map[int]map[int]bool)
    chk = make(map[int]bool)

    for i := 0; i < m; i++ {
        var x, y, z int
        fmt.Scan(&x, &y, &z)
        x--
        y--
        if _, ok := mp[x]; !ok {
            mp[x] = make(map[int]bool)
        }
        mp[x][y] = true
        if _, ok := mp[y]; !ok {
            mp[y] = make(map[int]bool)
        }
        mp[y][x] = true
    }

    var sum int
    for i := 0; i < n; i++ {
        sum += search(i)
    }
    fmt.Println(sum)
}

func search(pos int) int {
    if b, ok := chk[pos]; ok && b {
        return 0
    }
    chk[pos] = true
    for k, _ := range mp[pos] {
        search(k)
    }
    return 1
}