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(&:to_i)
ans = 0
check = Array.new(n,-1)
card_s = Array.new(n).map{Array.new()}
card_d = Array.new(n).map{Array.new()}
for i in 0..m-1
  inst = gets.split.map(&:to_i)
  if inst[2] % 2 == 0
    card_s[inst[0]-1].push(inst[1]-1)
    card_s[inst[1]-1].push(inst[0]-1)
  else
    card_d[inst[0]-1].push(inst[1]-1)
    card_d[inst[1]-1].push(inst[0]-1)
  end
end

for i in 0..n-1
  if check[i] == -1
    ans += 1
    check[i] = 0
    if card_s[i].length != 0
      for j in 0..card_s[i].length-1
        check[card_s[i][j]] = 0
      end
    end
    if card_d[i].length != 0
      for j in 0..card_d[i].length-1
        check[card_d[i][j]] = 1
      end
    end
  else
    if card_s[i].length != 0
      for j in 0..card_s[i].length-1
        check[card_s[i][j]] = check[i]
      end
    end
    if card_d[i].length != 0
      for j in 0..card_d[i].length-1
        check[card_d[i][j]] = (check[i]-1).abs
      end
    end
  end
end
puts ans