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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php



fscanf(STDIN, "%d%d", $N, $M);

$map = array_fill(1,$N,[]);
for($i=0;$i<$M;$i++){
    $tmp = explode(" ", trim(fgets(STDIN)));
    $map[$tmp[0]][$tmp[1]] = $tmp[2];
    $map[$tmp[1]][$tmp[0]] = $tmp[2];
}
$ans = 0;
for($i=1;$i<=$N;$i++) {
    if(isset($ans_map[$i])) {
        continue;
    }
    $start = $i;
    $queue = [];
    $q = 0;
    $ans++;
    $ans_map[$i] = $ans;
    if(count($map[$start]) === 0){
        $ans_map[$i] = $ans;
    }
//初期キューの登録
    getQueue($map[$start], $ans);
    while (isset($queue[$q])) {
        getQueue($map[$queue[$q][0]], $queue[$q][1]);
        unset($queue[$q]);
        $q++;
    }
}
//回答出力
echo $ans;


/**
 * @param array $array
 * @param int $last_vec
 * @param int $count
 * @return int
 */
function getQueue(array $array, int $color)
{
    global $queue, $ans_map;
    foreach ($array as $key => $value) {
        if (!isset($ans_map[$key])) {
            $ans_map[$key] = $color;
            $queue[] = [$key, $color];
        }
    }

    return 0;

}