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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {

	private void solve() {
		Scanner in = new Scanner(System.in);
		int N = in.nextInt();
		int M = in.nextInt();
		UnionFind tree = new UnionFind(N);
		for(int i=0; i<M; i++) {
			int X = in.nextInt()-1;
			int Y = in.nextInt()-1;
			int Z = in.nextInt();
			tree.unit(X, Y);
		}
		System.out.println(tree.countRoots());
	}
	
	class UnionFind{
		int[] parent;
		int[] depth;
		
		public UnionFind(int eNum){
			parent = new int[eNum];
			depth = new int[eNum];
			for(int i=0;i<eNum;i++){
				parent[i] = i;
			}
		}
		
		public int getRoot(int x){
			if(parent[x]==x) return x;
			return parent[x] = getRoot(parent[x]); // press
		}
		
		public void unit(int x,int y){
			x = getRoot(x);
			y = getRoot(y);
			if(x==y) return;
			if(depth[x]<depth[y]){
				parent[x] = y;
			}else{
				parent[y] = x;
				if(depth[x]==depth[y]) depth[x]++;
			}
		}
		
		public boolean same(int x,int y){
			return getRoot(x)==getRoot(y);
		}
		
		public int countRoots() {
			int count = 0;
			for(int i=0; i<parent.length; i++) {
				if(parent[i] == i) count ++;
			}
			return count;
		}
	}

	public static void main(String[] args) {
		new Main().solve();
	}
}