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)

#!/usr/bin/env php
<?php
// Generated by 1.1.4 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)

function genInputs() {
    while(($input = rtrim(fgets(STDIN))) !== false) {
        foreach (explode(' ', $input) as $v) {
            yield $v;
        }
    }
}
function getNext($gen) {
    $value = $gen->current();
    $gen->next();
    return $value;
}
$gen = genInputs();

$N = (int)getNext($gen);
$M = (int)getNext($gen);
$hints = [];
$hint_counts = array_fill(0, $N, 0);
for ($i = 0; $i < $M; $i++) {
    $X = (int)getNext($gen);
    $Y = (int)getNext($gen);
    $Z = (int)getNext($gen);

    $hints[$X][$Y] = true;
    $hints[$Y][$X] = true;
}
$clear = array_fill(0, $N, false);
arsort($hint_counts);
$magic = 0;
$chain = function($k) use($hints, &$clear, &$chain) {
    if ($clear[$k]) {
        return;
    }
    $clear[$k] = true;
    if (!isset($hints[$k])) {
        return;
    }
    foreach ($hints[$k] as $v => $tr) {
        $chain($v);
    }
};
for ($i = 1; $i <= $N; $i++) {
    if ($clear[$i]) {
        continue;
    }
    $magic++;
    if (!isset($hints[$i])) {
        continue;
    }
    $chain($i);
}
echo $magic.PHP_EOL;