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: Wrong Answer)

import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] arr = sc.nextLine().split(" ");
		int n = Integer.parseInt(arr[0]);
		int m = Integer.parseInt(arr[1]);
		ArrayList<LinkedList<Integer>> graph = new ArrayList<LinkedList<Integer>>();
		for(int i=0; i<n; i++) {
			graph.add(new LinkedList<Integer>());
		}
		for(int i=0; i<m; i++) {
			arr = sc.nextLine().split(" ");
			int x = Integer.parseInt(arr[0]);
			int y = Integer.parseInt(arr[1]);
			graph.get(x-1).add(y-1);
		}
		sc.close();


		int count = 0;
		int[] segment = new int[n];
		Arrays.fill(segment, -1);
		for(int i=0; i<n; i++) {
			if (segment[i] == -1) {
				segment[i] = count++;
			}
			for(int j: graph.get(i)) {
				segment[j] = segment[i];
			}
		}

		System.out.println(count);
	}
}