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: Wrong Answer)

import sys
sys.setrecursionlimit(100000)


N, M = [int(x) for x in input().split()]


# Union Find
# N = 100
PARENT = list(range(N))

def root(n):
    if PARENT[n] == n:
        return n
    else:
        ret = root(PARENT[n])
        PARENT[n] = ret
        return ret

def same(n1, n2):
    return root(n1) == root(n2)

def unite(n1, n2):
    n1 = root(n1)
    n2 = root(n2)
    if n1 == n2:
        return
    PARENT[n1] = n2

used = set()

for i in range(M):
    x, y, z = [int(x) for x in input().split()]
    x -= 1
    y -= 1
    used.add(x)
    used.add(y)
    rootX = root(x)
    rootY = root(y)
    if z % 2 == 0:
        unite(x, y)

uf = {root(n) for n in used}

ans = (len(uf) + 1) // 2 + (N - len(used))
print(ans)