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 Node:
    def __init__(self):
        self.is_parent = True
        self.parent = None

def root(node):
    depth = 0
    while node.parent != None:
        node = node.parent
        depth += 1
    return node, depth

N, M = map(int, input().split())

roots = [Node() for i in range(N)]
count = N

for i in range(M):
    x, y, z = map(int, input().split())
    x = roots[x-1]
    y = roots[y-1]
    if x.is_parent and y.is_parent:
            y.is_parent = False
            y.parent = x
            count -= 1
    else:
        root_x, depth_x = root(x)
        root_y, depth_y = root(y)
        if root_x != root_y:
            if depth_x >= depth_y:
                root_y.is_parent = False
                root_y.parent = root_x
                count -= 1
            else:
                root_x.is_parent = False
                root_x.parent = root_y
                count -= 1

print(count)