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++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define INF 1LL<<62
#define inf 1000000007

ll n,k;vector<ll>ch[100010];
bool ans[100010];
void dep(ll now,ll s){
	if(now!=s&&ch[now].size()==1){
		return ;
	}
	for(ll i=0;i<ch[now].size();i++){
		ll next=ch[now][i];
		if(ans[next]==true){
			continue;
		}
		ans[next]=true;
		dep(next,s);
	}
}
int main() {
	cin>>n>>k;
	for(ll i=0;i<k;i++){
		ll x,y,z;
		cin>>x>>y>>z;
		x--;y--;
		ch[x].push_back(y);
		ch[y].push_back(x);
	}
	ll ans2=0;
	for(ll i=0;i<n;i++){
		if(ans[i]==true){
			continue;
		}
		ans2++;
		dep(i,i);
	}
	cout <<ans2;
	// your code goes here
	return 0;
}