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 <string>
#include <algorithm>
#include <cstdio>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <numeric>
#include <cmath>

using namespace std;

typedef long long int ll;
typedef pair<int,int> P;

#define all(x) x.begin(),x.end()

const ll mod = 1e9+7;
const ll INF = 1e9;
const ll MAXN = 1e9;

struct union_find{
  vector<int> par,r;

  union_find(int n) : par(n),r(n){init(n);}

  void init(int n){
    for(int i = 0; i < n; i++) par[i] = i;
    for(int i = 0; i < n; i++) r[i] = 0;
  }

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

  void unite(int x,int y){
    x = find(x);
    y = find(y);
    if(x == y) return;
    if(r[x] < r[y]){
      par[x] = y;
    }else{
      par[y] = x;
      if(r[x] == r[y]) r[x]++;
    }
  }

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

int main()
{
	int n,m;
	cin>>n>>m;
	vector<int> x(m),y(m);
	for(int i = 0; i < m; i++){
		int z;
		cin>>x[i]>>y[i]>>z;
	}
	union_find uf(n);
	for(int i = 0; i < m; i++){
		x[i]--;
		y[i]--;
		if(!uf.same(x[i],y[i]))
			uf.unite(x[i],y[i]);
	}

	int ans=0;
	for(int i = 0; i < n; i++){
		if(uf.par[i]==i)
			ans++;
	}
	cout<<ans<<endl;

	return 0;
}