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 Ruby (2.3.3) (judge verdict: Runtime Error)

n, m = gets.chomp!.split(" ").map!(&:to_i)
xyz = Array.new(m) {|index| Array.new(0, m) }

xyzs = {}
xyz.each.with_index(1) do |xyz, i|
    x_i, y_i, z_i = gets.chomp!.split(" ").map!(&:to_i)
    xyzs[i] = {
        x: x_i,
        y: y_i,
        z: z_i,
    }
end

$dic = {}
require 'pp'
1.upto(n) do |i, _|
    $dic[i] = nil
end


def find_next(i, count = 0)
    if $dic[i].nil?.!
        find_next($dic[i])
    else
        return i, count
    end
end

xyzs.each do |i, xyz|
    i, _ = find_next(xyz[:x])
    $dic[i] = xyz[:y]
end

count = 0

$dic.count do |key, val|
    if val == nil || key == val 
        count+= 1
    end
end

puts count