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::cmp;
use std::collections::BinaryHeap;
use std::collections::HashMap;

fn read_line() -> String {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).ok();
    buf
}

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

impl UnionFind {
    fn new(n : usize)-> UnionFind {
        let mut par = Vec::with_capacity(n);
        for i in 0..n {
            par.push(i);
        }
        UnionFind {
            parent: par,
            size: vec![1; n]
        }
    }

    fn union(&mut self, l: usize, r: usize) {
        let mut lp = self.get_par(l);
        let mut rp = self.get_par(r);

        if lp != rp {
            self.parent[lp] = rp;
            self.size[rp] += self.size[lp];
        }
        
    }

    fn get_par(&mut self, tar: usize) -> usize {
        let mut par = tar;
        while self.parent[par] != par {
            par = self.parent[par];
        }
        self.parent[tar] = par;
        par
    }

    fn get_par_size(&mut self, tar: usize) -> usize {
        let par = self.get_par(tar);
        self.size[tar]
    }

    fn is_parent(&self, x: usize) -> bool {
        self.parent[x] == x
    }
}

fn main() {
    let line: Vec<usize> = read_line().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = line[0];
    let m = line[1];

    let mut uf = UnionFind::new(n);
    for i in 0..m {
        let line: Vec<usize> = read_line().split_whitespace().map(|s| s.parse().unwrap()).collect();
        let a = line[0] - 1;
        let b = line[1] - 1;

        uf.union(a,b);
    }

    let mut ans = 0;
    for i in 0..n {
        if uf.is_parent(i) {
            ans += 1;
        }
    }
    println!("{}", ans);
}