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 PyPy3 (2.4.0) (judge verdict: Runtime Error)

class uf_tree():

    def __init__(self,n):
        self.n = n
        self.par = [i for i in range(n)]

    def indep(self):
        dep =0
        for i in range(self.n):
            if i == self.par[i]:
                dep += 1

        return dep

    def unite(self,child,mas):
        if self.root(child) == self.root(mas):
            return
        else:
            self.par[self.root(child)] = self.root(self.mas)

    def root(self,i):
        if self.par[i] == i:
            return i
        else:
            self.par[i] = self.root(self.par[i])
            return self.par[i]

    def same(self,x,y):
        if self.root(x) == self.root(y):
            return True
        else:
            return False



n,m = map(int,input().split())
uf = uf_tree(n+1)
for i in range(m):
    x,y,z = map(int,input().split())
    uf.unite(x,y)

print(uf.indep()-1)