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 PyPy3 (7.3.0) (judge verdict: Accepted)

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

import sys
sys.setrecursionlimit(10**9) #再帰の上限をあげる

root=[-1 for i in range(n+1)] #自分が親ならグループの人数のマイナス倍を、そうでないなら（元）親の番号を示す
dep=[1]*(n+1)
def r(x):   #親は誰？
    if root[x]<0:
        return x
    else:
        root[x]=r(root[x])
        return root[x]

def unite(x,y):
    x=r(x)
    y=r(y)
    if x==y:
        return
    if dep[x]==dep[y]:
        dep[x]+=1
    if dep[x]<dep[y]:
        x,y=y,x
    root[x]+=root[y]
    root[y]=x

for i in range(m):
    x,y,z=map(int,input().split())
    unite(x,y)


g=[0]*(n+1)
for i in range(1,n+1):
    g[r(i)]+=1
ans=0
for i in range(n+1):
    if g[i]>0:
        ans+=1
print(ans)