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 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#define ll long long int
#define lim 100010
#define INF 1e9
#define MIN(x,y) ((x)<(y)?(x):(y))
#define MAX(x,y) ((x)<(y)?(y):(x))
#define ABS(x) ((x)>0?(x):-(x))
int p[lim],rank[lim];

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

void unit(int x,int y){
	x=find(x);
	y=find(y);
	if(x==y)return;
	if(rank[x]<rank[y])p[x]=y;
	else{
		p[y]=x;
		if(rank[x]==rank[y])rank[x]++;
	}
}

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

int main(void){
	int n,m;
	scanf("%d%d",&n,&m);
	int x,y,z;
	for(int i=0;i<n;i++){
		p[i]=i;
		rank[i]=0;
	}
	for(int i=0;i<m;i++){
		scanf("%d%d%d",&x,&y,&z);
		x--;
		y--;
		unit(x,y);
	}
	bool known[n];
	for(int i=0;i<n;i++)known[i]=false;
	int ans=0;
	for(int i=0;i<n;i++){
		if(!known[p[i]]){
			ans++;
			known[p[i]]=true;
		}
	}
	printf("%d",ans);
	return 0;
}