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>
#define cout16 cout << setprecision(16) 
#define rep(i,n) for(int i=0;i<n;i++ )
#define rep2(i,f,n) for(int i=f;i<n;i++ )
#define MAX(A) *max_element(A.begin(),A.end())
#define MIN(A) *min_element(A.begin(),A.end())
#define SORT(A) sort(A.begin(),A.end())
#define REV(A) reverse(A.begin(),A.end())
typedef long long int ll;
using vi = std::vector<int>;
using vvi = std::vector<std::vector<int>>;
using vll = std::vector<ll>;
using vvll = std::vector<std::vector<ll>>;
using P = std::pair<int,int>;
using vp = std::vector<P>;
using namespace std;
#define INF 1001001001
#define LL_INF 1001001001001001001

vi root(100005);
int find(int x){
	if(root[x]==x) return x;
	else return root[x]=find(root[x]);
}
bool same(int x, int y){
	return find(x)==find(y);
}	
void union_tree(int x,int y, int &n_trees){
	if(same(x,y)) return;
	int rt_x = root[x];
	int rt_y = root[y];	
	root[rt_y] = rt_x;
	n_trees--;
}

int main(void) {
	int n,m; cin >> n >> m;
	int n_trees = n;
	rep(i,n) root[i] = i;
	rep(i,m){
		int x,y,z; cin >> x >> y >> z;
		x--; y--;
		union_tree(x,y,n_trees);
	}
	cout << n_trees << endl;
}