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 Python (3.4.3) (judge verdict: Accepted)

class UnionFind:

    def __init__(self, n: int):
        self._n = n
        self._parents = [i for i in range(n)]
        self._rank = [1 for _ in range(n)]

    def unite(self, x: int, y: int) -> None:
        px = self.find(x)
        py = self.find(y)

        # 一致していないときはリンクをつける
        if px != py:
            self._link(px, py)

    def _link(self, x: int, y: int):
        if self._rank[x] < self._rank[y]:
            self._parents[x] = y
        elif self._rank[x] > self._rank[y]:
            self._parents[y] = x
        else:
            self._parents[x] = y
            self._rank[y] += 1

    def same(self, x: int, y: int) -> bool:
        px = self.find(x)
        py = self.find(y)
        return px == py

    def find(self, x: int) -> int:
        if self._parents[x] == x:
            return x

        self._parents[x] = self.find(self._parents[x])
        return self._parents[x]



n, m = map(int, input().split())

uf = UnionFind(n)

for _ in range(m):
    x, y, _ = map(int, input().split())
    uf.unite(x - 1, y - 1)

s = set()
for i in range(0, n):
    s.add(uf.find(i))

print(len(s))