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 proconio::{fastout, input, marker::Usize1};

fn dfs(graph: &Vec<Vec<usize>>, seen: &mut Vec<bool>, v: usize) {
    seen[v] = true;
    for next in graph[v].iter() {
        if !seen[*next] {
            dfs(graph, seen, *next);
        }
    }
}

#[fastout]
fn main() {
    input! {
        n: usize,
        m: usize,
        graph_base: [(Usize1, Usize1, i64); m]
    }

    let mut graph: Vec<Vec<usize>> = Vec::new();
    for _ in 0..n {
        graph.push(Vec::new());
    }
    for edge in graph_base.iter() {
        graph[edge.0].push(edge.1);
        graph[edge.1].push(edge.0);
    }

    let mut seen = vec![false; n];
    let mut count = 0;
    for v in 0..n {
        if !seen[v] {
            dfs(&graph, &mut seen, v);
            count += 1;
        }
    }

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