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: Runtime Error)

'use strict';

function main(stdin) {
  const input = stdin.split('\n');
  const param = input.shift().split(' ').map(v => parseInt(v, 10));
  const N = param[0];
  const M = param[1];
  const pairs = input.map(p => p.split(' ').map(v => parseInt(v, 10)));
  
  const arrived = [];
  const refs = [];

  for (let i = 1; i <= N; ++i) {
    arrived[i] = false;
    refs[i] = [];
  }

  pairs.forEach(p => {
    refs[p[0]].push(p[1]);
  });

  function search(n) {
    arrived[n] = true;

    if (!refs[n].length) return true;

    search(refs[n].shift());
  }

  let i = 1;
  let ans = 0;
  while (i <= N) {
    ++ans;
    search(i);
    while (arrived[i]) ++i;
  }
  
  console.log(ans);
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));