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::input;
use proconio::marker::Usize1;
use std::collections::HashSet;

struct UnionFind {
    parent: Vec<usize>,
    rank: Vec<i32>,
}

impl UnionFind {
    fn new(n: usize) -> Self {
        UnionFind {
            parent: (0..n).map(|i| i).collect(),
            rank: vec![0; n],
        }
    }

    fn find(&mut self, n: usize) -> usize {
        if self.parent[n] == n {
            return n;
        };
        self.parent[n] = self.find(self.parent[n]);
        self.parent[n]
    }

    fn same(&mut self, n: usize, m: usize) -> bool {
        self.find(n) == self.find(m)
    }

    fn unit(&mut self, n: usize, m: usize) {
        let n = self.find(n);
        let m = self.find(m);
        if n == m {
            return;
        }
        if self.rank[n] > self.rank[m] {
            self.parent[m] = n;
        } else {
            self.parent[n] = m;
            if self.rank[n] == self.rank[m] {
                self.rank[n] += self.rank[m];
            }
        }
    }
}

fn main()
{
    input! {
    n:usize,
    m:usize,
    v:[(Usize1,Usize1,i32);m],
    }

    let mut uf = UnionFind::new(n);
    for &(a, b, _) in v.iter() {
        uf.unit(a, b);
    }

    let mut id: HashSet<usize> = (0..n).into_iter().map(|i| uf.find(i)).collect();
    println!("{}", id.iter().count());
}