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: Accepted)


#N=gets.to_i
#S=gets.chomp
#A=(0...N).map{gets.to_i}
#sum=A.inject(&:+)
#B=gets.split.map(&:to_i)




class WeightedUnionFind
  @par=[] # 親の番号
  @ws=[]  # 親との重みの差
  
  def initialize(n)
      @par = (0...n).to_a
      @ws  = Array.new(n,0)
  end
  
  def find(x)
      if @par[x]==x
          return x
      else
          parent = find(@par[x])
          @ws[x] += @ws[@par[x]]
          @par[x]=parent
          return parent
      end
  end
  
  def weight(x)
      find(x) 
      return @ws[x]
  end
  
  def union(x,y,w) # x <-(w)- y (x + w = y)
      w += weight(x)
      w -= weight(y)
      x = find(x)
      y = find(y)
      
      if x != y
          @par[y] = x
          @ws[y] = w
          return true
      else
          return false
      end
  end
  
  def same(x, y)
      return find(x) == find(y)
  end
  
  def diff(x,y) # x - y を求める. 比較不能ならnil
      return nil if !same(x, y)
      return weight(x) - weight(y)
  end
end


N,M=gets.split.map(&:to_i)
uf=WeightedUnionFind.new(N)

M.times do
  x,y,z=gets.split.map(&:to_i)
  uf.union(x-1,y-1,1)
end


parcount={}
N.times do |i|
  parcount[uf.find(i)]=1
end
puts parcount.size