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.time.Year;
import java.util.*;
import java.util.Scanner;
import java.util.stream.Collectors;

public class Main {

    // input
    static int n;
    static int m;
    static int x[];
    static int y[];
    static int z[];

    /**
     * input
     */
    static void input(){
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();
        x = new int[m];
        y = new int[m];
        z = new int[m];

        for(int i=0;i<m;i++){
            x[i] = sc.nextInt();
            y[i] = sc.nextInt();
            z[i] = sc.nextInt();
        }
        sc.close();
    }
 

    // global
    static int[] ans;

    private static class UnionFindTree {

        private static int[] par;
        private static int[] rank;
        private static int size;

        UnionFindTree(int n){
            this.par = new int[n];
            this.rank = new int[n];

            for(int i=0;i<n;i++){
                this.par[i] = i;
            }
            this.size = n;
        }

        int find(int x) {
            if (this.par[x] == x) {
                return x;
            } else {
                return par[x] = this.find(par[x]);
            }
        }

        void unite(int x, int y) {
            x = this.find(x);
            y = this.find(y);
            if (x == y) return;

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

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

        int size(){
            return this.size;
        }
    }


    /**
     * solver
     */
    static void solve(){

        UnionFindTree uft = new UnionFindTree(2*(n+1));

        for(int i=0;i<m;i++){
            if (z[i] % 2 == 1) {
                uft.unite(x[i], y[i]+n);
                uft.unite(x[i]+n, y[i]);
            } else {
                uft.unite(x[i], y[i]);
                uft.unite(x[i]+n,y[i]+n);
            }
        }

        System.out.println((uft.size()-2)/2);
    }


    public static void main(String args[]) {

        input();

        solve();
    }
}