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 (1.15.1) (judge verdict: Accepted)

use std::collections::HashMap;

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|s| s.parse().ok().unwrap())
        .collect()
}

fn main() {
    let input = read_vec::<usize>();
    let (n, m) = (input[0], input[1]);
    let mut map = HashMap::new();
    for _ in 0..m {
        let input = read_vec::<usize>();
        let (x, y) = (input[0]-1, input[1]-1);
        map.entry(x).or_insert_with(|| vec![]).push(y);
        map.entry(y).or_insert_with(|| vec![]).push(x);
    }
    let mut used = vec![false; n];
    

    let mut count = 0;
    for i in 0..n {
        if used[i] {
            continue;
        }
        count += 1;
        dfs(i, &map, &mut used);
    }

    println!("{}", count);
}

fn dfs(index: usize, map: &HashMap<usize, Vec<usize>>, used: &mut Vec<bool>) {
    used[index] = true;
    if let Some(val) = map.get(&index) {
        for &key in val.iter() {
            if used[key] {
                continue;
            }
            dfs(key, map, used);
        }
    }
}