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: Wrong Answer)

N,M = gets.split.map {|x| x.to_i}
arrs = []
M.times {
  x,y,z = gets.split.map {|x| x.to_i}
  xi = -1
  yi = -1
  arrs.each_with_index { |arr,i|
    if arr.include?(x)
      xi = i
    end
    if arr.include?(y)
      yi = i
    end
  }
  if (xi != -1) and (yi != -1)
    if xi != yi
      if xi < yi
        d = arrs.delete_at(yi)
        arrs[xi] += d
      else
        d = arrs.delete_at(xi)
        puts d
        arrs[yi] += d
      end
    end
  elsif (xi == -1) and (yi == -1)
    arrs << [x,y]
  elsif (xi != -1)
    arrs[xi].push(y)
  else
    arrs[yi].push(x)
  end
  
}

c = []
N.times { |i|
  c << i+1
}
arrs.each { |arr|
  c = c - arr
}
#p c.size
puts arrs.size + c.size