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)

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

items = []
ans = 0
visible = set()

for i in range(M):
    x, y, z = map(int, input().split())
    visible.add(x)
    visible.add(y)
    items.append((x, y, z))
unvisible = set([i for i in range(1, N + 1)]) - visible
ans += len(unvisible)


def f(num):
    know = set()
    cnt = 0
    for x, y, z in items:
        if x in know:
            # tmp = know[x]
            # if tmp + z % 2 == 0:
            #     know[y] = 2
            # else:
            #     know[x] = 1
            know.add(y)
            continue
        elif y in know:
            # tmp = know[y]
            # if tmp + z % 2 == 0:
            #     know[x] = 2
            # else:
            #     know[x] = 1
            know.add(x)
            continue
        else:
            cnt += 1
            know.add(x)
            know.add(y)
    if cnt <= num:
        return True
    else:
        return False


ok = N - ans
ng = -1

while abs(ok - ng) > 1:
    mid = (ok + ng) // 2
    if f(mid):
        ok = mid
    else:
        ng = mid
print(ans + ok)