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: Wrong Answer)

<?php
class Line {
    protected $lineData;
    protected $pointer;
    public function __construct(array $line)
    {
        $this->lineData = $line;
        $this->pointer = 0;
        $this->count = count($line);
    }

    public function next()
    {
        if ($this->count > $this->pointer) {
            return $this->lineData[$this->pointer++];
        }
        return false;
    }
}

class IOW {
    /**
     * @return Line
     */
    public static function nl()
    {
        $str = trim(fgets(STDIN));
        return new Line(explode(' ', $str));
    }

    public static function out($data)
    {
        print_r ($data . PHP_EOL);
    }
}

$line = IOW::nl();
$n = $line->next();
$m = $line->next();
$parents = [];
for ($i = 1; $i <= $n; $i++) {
    $parents[$i] = $i;
}

for ($i = 0; $i < $m; $i++) {
    $line = IOW::nl();
    $A1 = $line->next();
    $A2 = $line->next();
    if ($A1 < $A2) {
        $parents[$A2] = $parents[$A1];
    } else {
        $parents[$A1] = $parents[$A2];
    }
}

IOW::out(count(array_unique($parents)));