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};
struct UnionFind{
    par : Vec<usize>,
    n_tree : usize,
}

impl UnionFind{
    pub fn new(n: usize) -> Self{
        let par : Vec<usize>= (0..n).collect();
        UnionFind{
            par,
            n_tree: n,
        }
    }

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

        self.par[x] = self.root(self.par[x]);
        self.par[x]
    }

    pub fn unite(&mut self, x: usize, y: usize){
        let rx = self.root(x);
        let ry = self.root(y);

        if rx == ry{
            return;
        }
        self.n_tree -= 1;
        self.par[rx] = ry;
    }

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

    pub fn num_tree(&self) -> usize{
        self.n_tree
    }

}

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

    let mut uf = UnionFind::new(n);

    for e in &tu{
        let x = e.0 - 1;
        let y = e.1 - 1;

        uf.unite(x, y);
    }

    println!("{}",uf.num_tree());
}