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
$input = explode(' ', trim(fgets(STDIN)));

$n = (int)$input[0];
$m = (int)$input[1];

$as = [];
$parent = [];
for ($i=1; $i <= $n; $i++) { 
	$as[$i] = false;
	$parent[$i] = $i;
}

for ($i=0; $i < $m; $i++) { 
	$input = explode(' ', trim(fgets(STDIN)));
	$x = (int)$input[0];
	$y = (int)$input[1];
	// $z = (int)$input[2];
	// $as[$x] = true;
	// $as[$y] = true;
	if (getParent($y) < getParent($x)) {
		$parent[getParent($x)] = getParent($y);
	}else{
		$parent[getParent($y)] = getParent($x);
	}
}
// foreach ($parent as $key => $value) {
// 	echo $key . ': ' . $value . PHP_EOL;
// }

// $undefined = 0;
$groupHead = [];
for ($i=1; $i <= $n; $i++) { 
	$groupHead[getParent($i)] = true;
}
echo count($groupHead);




function getParent($num){
	global $parent;
	if ($parent[$num] === $num) {
		return $num;
	}else{
		$parent[$num] = getParent($parent[$num]);
		return $parent[$num];
	}
}