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::io::*;
use std::str::FromStr;

pub fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}

struct UnionFind {
    parent: Vec<usize>,
    size: Vec<usize>,
}

impl UnionFind {
    fn new(n: usize) -> UnionFind {
        // initialize
        let mut v: Vec<usize> = vec![];
        for i in 0..n + 1 {
            v.push(i)
        }
        let mut s: Vec<usize> = vec![1; n + 1];

        UnionFind { parent: v, size: s }
    }

    fn root(&self, x: usize) -> usize {
        if self.parent[x] == x {
            return x;
        } else {
            return self.root(self.parent[x]);
        }
    }

    fn size(&self, a: usize) -> usize {
        let ra = self.root(a);
        self.size[ra]
    }

    fn unite(&mut self, a: usize, b: usize) {
        let mut ra = self.root(a);
        let mut rb = self.root(b);
        if ra == rb {
            return;
        }
        if self.size[ra] < self.size[rb] {
            std::mem::swap(&mut ra, &mut rb)
        };
        self.size[ra] += self.size[rb];
        self.parent[rb] = ra;
    }

    fn same(&self, a: usize, b: usize) -> bool {
        let ra = self.root(a);
        let rb = self.root(b);
        ra == rb
    }
}

use std::collections::HashSet;

fn main() {
    let n: usize = read();
    let m: usize = read();
    let mut uf = UnionFind::new(n);
    let mut uniq = HashSet::new();

    let mut a: Vec<(usize, usize, usize)> = vec![];

    for _ in 0..m {
        a.push((read(), read(), read()));
    }
    for i in 0..a.len() {
        uf.unite(a[i].0, a[i].1);
    }

    for i in 0..n {
        uniq.insert(uf.root(i + 1));
    }
    println!("{}", uniq.len());
}