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)

#![allow(unused_imports)]
#![allow(unused_macros)]
use std::cmp::{ min, max };

macro_rules! ewriteln {
    ($($args:expr),*) => { let _ = writeln!(&mut std::io::stderr(), $($args),*); };
}
macro_rules! trace {
    ($x:expr) => { ewriteln!(">>> {} = {:?}", stringify!($x), $x) };
    ($($xs:expr),*) => { trace!(($($xs),*)) }
}
macro_rules! put {
    ($x:expr) => { println!("{}", $x) };
    ($x:expr, $($xs:expr),*) => { print!("{} ", $x); put!($($xs),*) }
}

#[allow(dead_code)]
const M: i64 = 1_000_000_007;

#[derive(Debug, Clone)]
enum UF { Root(usize), Child(usize) }

#[derive(Debug)]
struct UnionFind { table: Vec<UF> }
impl UnionFind {

    fn new(n: usize) -> UnionFind {
        UnionFind { table: vec![UF::Root(1); n], }
    }

    fn root(&mut self, x: usize) -> usize {
        match self.table[x] {
            UF::Root(_) => x,
            UF::Child(parent) => {
                let root = self.root(parent);
                self.table[x] = UF::Child(root);
                root
            }
        }
    }

    fn is_same(&mut self, x: usize, y: usize) -> bool {
        self.root(x) == self.root(y)
    }

    fn size(&mut self, x: usize) -> usize {
        let r = self.root(x);
        match self.table[r] {
            UF::Root(size) => size,
            UF::Child(_) => 0
        }
    }

    fn merge(&mut self, x: usize, y: usize) {
        let root_x = self.root(x);
        let root_y = self.root(y);
        if root_x != root_y {
            let size_x = self.size(root_x);
            let size_y = self.size(root_y);
            let (i, j) = if size_x > size_y {
                (root_x, root_y)
            } else {
                (root_y, root_x)
            };
            self.table[i] = UF::Root(size_x + size_y);
            self.table[j] = UF::Child(i);
        }
    }
}

fn main() {
    let mut sc = Scanner::new();
    let n: usize = sc.cin();
    let mut uf = UnionFind::new(n);
    let m: usize = sc.cin();
    for _ in 0..m {
        let x: usize = sc.cin::<usize>() - 1;
        let y: usize = sc.cin::<usize>() - 1;
        let _: usize = sc.cin();
        uf.merge(x, y);
    }
    use std::collections::HashSet;
    let mut hs = HashSet::new();
    for i in 0..n {
        hs.insert( uf.root(i) );
    }
    put!(hs.len());
}

use std::io::{self, Write};
use std::str::FromStr;
use std::collections::VecDeque;

struct Scanner { stdin: io::Stdin, buffer: VecDeque<String>, }
impl Scanner {
    fn new() -> Scanner { Scanner { stdin: io::stdin(), buffer: VecDeque::new() } }
    fn cin<T: FromStr>(&mut self) -> T {
        while self.buffer.len() == 0 {
            let mut line = String::new();
            let _ = self.stdin.read_line(&mut line);
            for w in line.split_whitespace() {
                self.buffer.push_back(String::from(w));
            }
        }
        self.buffer.pop_front().unwrap().parse::<T>().ok().unwrap()
    }
}