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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>

int max_array_point(int ary[], int ary_num) {
  int i;
  int max = -1;
  int point = 0;
  for(i = 0; i < ary_num; i++) {
    if(max < ary[i]) {
      max = ary[i];
      point = i;
    }
  }
  return point;
}

int main() {
  int i;

  int n_val, m_val, x_val[100000], y_val[100000], z_val[100000];
  scanf("%d %d", &n_val, &m_val);
  for(i = 0; i < m_val; i++) scanf("%d %d %d", &x_val[i], &y_val[i], &z_val[i]);

  int *card_flag;
  card_flag = (int *)malloc(sizeof(int) * (n_val + 1));
  for(i = 0; i < n_val + 1; i++) card_flag[i] = 0;

  int *hint_flag;
  hint_flag = (int *)malloc(sizeof(int) * (m_val));
  for(i = 0; i < m_val; i++) hint_flag[i] = 0;

  int num_hint[100000 + 1] = {0};
  for(i = 0; i < m_val; i++) {
    num_hint[x_val[i]]++;
    num_hint[y_val[i]]++;
  }

  int num_magic = 0;
  int num_hint_max;
  while(1) {
    num_hint_max = max_array_point(num_hint, n_val + 1);
    if(card_flag[num_hint_max] == 0) {
      for(i = 0; i < m_val; i++) {
        if(hint_flag[i] == 0
         && (x_val[i] == num_hint_max || y_val[i] == num_hint_max)) {
          hint_flag[i] = 1;
          card_flag[x_val[i]] = 1;
          card_flag[y_val[i]] = 1;
        }
      }
      num_magic++;
    }
    num_hint[num_hint_max] = 0;
    int repeat_flag = 0;
    for(i = 1; i < n_val + 1; i++) {
      if(card_flag[i] == 0) repeat_flag++;
    }
    if(repeat_flag == 0) break;
    for(i = 0; i < m_val; i++) {
      if(card_flag[x_val[i]] == 1 && card_flag[y_val[i]] == 1) {
        hint_flag[i] = 1;
      }
    }
    repeat_flag = 0;
    for(i = 0; i < m_val; i++) {
      if(hint_flag[i] == 0) repeat_flag++;
    }
    if(repeat_flag == 0) break;
  }

  for(i = 1; i < n_val + 1; i++) {
    if(card_flag[i] == 0) num_magic++;
  }

  printf("%d\n", num_magic);

  return 0;
}