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::*;


struct UnionFind {
    forest: Vec<usize>
}


impl UnionFind {
    pub fn new(n: usize) -> UnionFind {
        UnionFind { forest: (0..n).collect() }
    }


    fn group(&mut self, mut i: usize) -> usize {
        let mut path = vec![];
        while self.forest[i] != i {
            path.push(i);
            i = self.forest[i]
        }
        for p in path { self.forest[p] = i }
        i
    }


    fn merge(&mut self, edges: Vec<(usize, usize)>) {
        for (l, r) in edges {
            let gl = self.group(l);
            let gr = self.group(r);
            if gl != gr {
                self.forest[gl] = gr
            }
        }
    }


    fn count(&mut self) -> usize {
        let mut cnt = 0;
        for i in 0..self.forest.len() {
            if self.forest[i] == i {
                cnt += 1
            }
        }
        cnt
    }
}



fn solve(buf: String) -> usize {
    let it: Vec<&str> = buf.split_whitespace().collect();
    let it: Vec<usize> = it.iter().map(|x| x.parse::<usize>().unwrap()).collect();
    let n = it[0];
    let m = it[1];
    let it = &it[2..];
    let mut edges = vec![];
    for i in 0..m {
        edges.push((it[3*i]-1, it[3*i+1]-1))
    }
    let mut uf = UnionFind::new(n);
    uf.merge(edges);
    uf.count()
}


fn main() {
    let mut buf = String::new();
    stdin().read_to_string(&mut buf).unwrap();
    println!("{}", solve(buf));
}