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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;
const int N=100005;
struct UnionFind
{
	int parent[N],rnk[N];
	UnionFind(int n)
	{
		for(int i=0;i<=n;i++)
		{
			parent[i]=i;
			rnk[i]=1;
		}
	}
	int root(int x)
	{
		if(parent[x]!=x)
			parent[x]=root(parent[x]);
		return parent[x];
	}
	void connect(int x,int y)
	{
		int rx=root(x),ry=root(y);
		if(rx==ry)
			return;
		if(rx>ry)
		{
			parent[ry]=rx;
			rnk[rx]+=rnk[ry];	
		} 
		if(rx<=ry)
		{
			parent[rx]=ry;
			rnk[ry]+=rnk[rx];
		}
	}
};
set<int>s;
int main()
{
	int n,m;
	scanf("%d%d",&n,&m);
	UnionFind uf(n);
	for(int i=1;i<=m;i++)
	{
		int x,y,z;
		scanf("%d%d%d",&x,&y,&z);
		uf.connect(x,y);
	}
	for(int i=1;i<=n;i++)
		s.insert(uf.root(i));
	printf("%d\n",s.size());
	return 0;
}