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.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {
	public static void main(String[] args) {
		try (Scanner sc = new Scanner(System.in)) {
			int n = sc.nextInt();
			int m = sc.nextInt();
			UnionFind uf = new UnionFind(n);
			for (int i = 0; i < m; i++) {
				int x = sc.nextInt() - 1;
				int y = sc.nextInt() - 1;
				int z = sc.nextInt();
				uf.unit(x, y);
			}
			Set<Integer> group = new HashSet<>();
			for (int i = 0; i < n; i++) {
				group.add(uf.root(i));
			}
			System.out.println(group.size());
		}
	}
}

class UnionFind {
	int[] par;
	int[] rank;

	UnionFind(int n) {
		par = new int[n];
		rank = new int[n];
		for (int i = 0; i < n; i++) {
			par[i] = i;
			rank[i] = 0;
		}
	}

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

	boolean same(int x, int y) {
		return root(x) == root(y);
	}

	void unit(int x, int y) {
		x = root(x);
		y = root(y);
		if (x == y) return;

		if (rank[x] < rank[y]) {
			par[x] = y;
		}
		else {
			par[y] = x;
			if (rank[x] == rank[y]) rank[x]++;
		}
	}
}