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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

var lines = [];
var readline = require('readline');

var rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

rl.on('line', function (x) {
    lines.push(x);
});

rl.on('close', function () {
    var N = Number(lines[0].split(" ")[0]);
    var M = Number(lines[0].split(" ")[1]);

    lines.shift();

    var XYZ = lines.map(i => i.split(" ").map(i => Number(i)))
    var check = Array(N).fill(-1); var ans = 0;

    XYZ.sort((a, b) => a[0] - b[0])

    while (XYZ.length) {
        var t = XYZ.shift();
        var x = t[0]; var y = t[1]; var z = t[2];

        if (check[x - 1] !== -1) { check[y - 1] = 1 }
        else if (check[y - 1] !== -1) { check[x - 1] = 1 }
        else { ans++; check[x - 1] = 1; check[y - 1] = 1 }
    }


    for (var i = 0; i < N; i++) {
        if (check[i] === -1) { ans++ }
    }
    console.log(ans);
});