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 <iostream>
#include <vector>
#include <algorithm>
#include <stack>
#include <queue>
#include <list>
#include <string>
#include <numeric>
#include <math.h>
#include <set>
#include <map>
#include <fstream>
#include <sstream>
#include <iterator>
#include <complex>
using namespace std;

typedef struct UnionFind
{
	vector<int> par;

	UnionFind(int N)
	{
		par.resize(N);
		for(int i=0; i<N; i++)
		{
			par[i] = i;
		}
	}

	int root(int x)
	{
		if(par[x]==x)
		{
			return x;
		}
		else
		{
			return par[x] = root(par[x]);
		}
	}

	void unite(int x, int y)
	{
		int rx = root(x);
		int ry = root(y);
		if(rx==ry)
		{
			return;
		}
		par[rx] = ry;
	}

	bool same(int x, int y)
	{
		return root(x) == root(y);
	}
}UnionFind;

int main()
{
	int N,M;
	cin>>N>>M;

	UnionFind tree(N);

	for(int i=0; i<M; i++)
	{
		int x,y,z;
		cin>>x>>y>>z;
		x--;
		y--;
		tree.unite(x,y);
	}

	set<int> s;

	for(int i=0; i<N; i++)
	{
		s.insert(tree.root(i));
	}

	cout<<s.size()<<endl;
	
	return 0;
}