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.*;

public class Main {
    private static int[] roots;
    
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        UnionFind uf = new UnionFind(n);
        
        while (m-- > 0) {
            int x = sc.nextInt() - 1;
            int y = sc.nextInt() - 1;
            sc.nextInt();
            uf.unite(x, y);
        }
        
        System.out.println(uf.connectedComponent());
    }
    
    public static class UnionFind {
        int[] par;
    
        UnionFind(int n) {
            par = new int[n];
            for (int i = 0; i < n; i++) {
                par[i] = i;
            }
        }
    
        int root(int x) {
            if (par[x] == x) return x;
            return root(par[x]);
        }
    
        void unite(int x, int y) {
            int rx = root(x);
            int ry = root(y);
            if (rx == ry) return;
            par[ry] = rx;
            printPar();
        }
    
        boolean same(int x, int y) {
            int rx = root(x);
            int ry = root(y);
            return rx == ry;
        }
        
        int connectedComponent() {
            Set<Integer> set = new HashSet<Integer>();
            for (int p : par) {
                set.add(p);
            }
            
            return set.size();
        }
        
        void printPar() {
            System.out.println(Arrays.toString(par));
        }
    }
}