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 Rust (1.42.0) (judge verdict: Accepted)

use std::cmp::*;
use std::io::*;

mod disjoint_set {
    pub struct DisjointSet {
        parent: Vec<usize>,
        size: Vec<usize>,
    }
    impl DisjointSet {
        pub fn new(n: usize) -> DisjointSet {
            DisjointSet {
                parent: (0..n).collect(),
                size: vec![1; n],
            }
        }
        pub fn root(&mut self, x: usize) -> usize {
            if x == self.parent[x] {
                x
            } else {
                let tmp = self.parent[x];
                self.parent[x] = self.root(tmp);
                self.parent[x]
            }
        }
        pub fn merge(&mut self, x: usize, y: usize) {
            let x = self.root(x);
            let y = self.root(y);
            if x == y {
                return;
            }
            if self.size[x] > self.size[y] {
                self.size[x] += self.size[y];
                self.parent[y] = x;
            } else {
                self.size[y] += self.size[x];
                self.parent[x] = y;
            }
        }
    }
}

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let m: usize = itr.next().unwrap().parse().unwrap();

    let mut ds = disjoint_set::DisjointSet::new(n);
    for _ in 0..m {
        let x: usize = itr.next().unwrap().parse::<usize>().unwrap() - 1;
        let y: usize = itr.next().unwrap().parse::<usize>().unwrap() - 1;
        let z: usize = itr.next().unwrap().parse().unwrap();
        ds.merge(x, y);
    }
    let mut ans = 0;
    let mut used = vec![false; n];
    for i in 0..n {
        if !used[ds.root(i)] {
            ans += 1;
            used[ds.root(i)] = true;
        }
    }
    println!("{}", ans);
}