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::io;
use std::str::FromStr;
use std::collections::HashSet;

fn input_tuple() -> (usize, usize) {
    let mut line: String = String::new();
    io::stdin().read_line(&mut line);
    let vec: Vec<usize> = line.split_whitespace().map(|s| s.parse().unwrap()).collect();
    (vec[0], vec[1])
}

fn input_tuple_three() -> (usize, usize, usize) {
    let mut line: String = String::new();
    io::stdin().read_line(&mut line);
    let vec: Vec<usize> = line.split_whitespace().map(|s| s.parse().unwrap()).collect();
    (vec[0], vec[1], vec[2])
}

#[derive(Debug, PartialEq, Clone)]
struct Node {
    parent: Option<usize>, 
    size: usize,
}

#[derive(Debug, PartialEq)]
pub struct UnionFind {
    tree: Vec<Node>,
}

impl UnionFind {
    pub fn new(n: usize) -> UnionFind {
        UnionFind {tree: vec![Node {parent: None, size: 1}; n]}
    }

    pub fn unite(&mut self, i: usize, j: usize) {
        let root_i = self.find(i);
        let root_j = self.find(j);
        if root_i == root_j {
            return
        }

        if self.tree[root_i].size < self.tree[root_j].size {
            self.tree[root_i].size += self.tree[root_j].size;
            self.tree[root_j].parent = Some(root_i);
        } else {
            self.tree[root_j].size += self.tree[root_i].size;
            self.tree[root_i].parent = Some(root_j);
        }

    }

    pub fn find(&mut self, i: usize) -> usize {
        match self.tree[i].parent {
            Some(p) => {
                let root = self.find(p);
                self.tree[i].parent = Some(root);
                root
            },
            None => i
        }
    }

    pub fn equiv(&mut self, i: usize, j: usize) -> bool {
        self.find(i) == self.find(j)
    }

    pub fn size(&mut self, i: usize) -> usize {
        let root = self.find(i);
        self.tree[root].size
    }
}

fn main() {
    let (n, m) = input_tuple();
    let mut union_find = UnionFind::new(n);
    for _ in 0..m {
        let (x, y, _) = input_tuple_three();
        union_find.unite(x - 1, y - 1);
    }
    let mut set: HashSet<usize> = HashSet::new();
    for i in 0..n {
        set.insert(union_find.find(i));        
    }
    println!("{}", set.len());
}