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)

import sys
input = sys.stdin.readline

class Unionfind:

    __slots__ = ['nodes','size']

    def __init__(self, n):
        self.nodes = list(range(n))
        self.size = [1]*n

    def root(self, x):
        if self.nodes[x] == x:
            return x
        else:
            root_x = self.root(self.nodes[x])
            self.nodes[x] = root_x
            return root_x

    def unite(self, x, y):
        x = self.root(x); y = self.root(y)
        if x == y:
            return
        if self.size[x] < self.size[y]:
            x, y = y, x
        self.size[x] += self.size[y]
        self.nodes[y] = x

    def same(self, x, y):
        return self.root(x) == self.root(y)

N,M = map(int,input().split())
info = [list(map(int,input().split())) for _ in range(M)]

uf = Unionfind(N)

for x,y,z in info:
    x -= 1
    y -= 1
    uf.unite(x,y)

for i in range(N):
    uf.root(i)

ans = len(list(set(uf.nodes)))
print(ans)