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 UnionFind:
    def __init__(self, max_size):
        self.parent = [i for i in range(max_size+1)]
        self.depth = [0 for _ in range(max_size+1)]
        self.cnt = [1 for i in range(max_size+1)]
    def find(self, x):
        if self.parent[x]==x:
            return x
        else:
            self.parent[x] = self.find(self.parent[x]) 
            return self.parent[x]
    
    def unite(self,x,y):
        x = self.find(x)
        y = self.find(y)
        if x==y:
            return
        elif self.depth[x]<self.depth[y]:
            self.parent[x] = y
            self.cnt[y] += self.cnt[x]
        else:
            self.parent[y] = x
            self.cnt[x]+=self.cnt[y]
            if self.depth[x]==self.depth[y]:
                self.depth[x]+=1
    def same(self, x, y):
        return self.find(x)==self.find(y)
    def size(self,x):
        return self.cnt[self.find(x)]

n,m = map(int,input().split())
utree = UnionFind(n+10)
for _ in range(m):
    x,y,z = map(int,input().split())
    utree.unite(x,y)
l = [utree.find(i) for i in range(1,n+1)]
print(len(set(l)))