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 (Clang 3.8.0) (judge verdict: Accepted)

#include <stdio.h>

int ans = 0;
int n, m;
int parent[100005];
int f[100005];

void init(void);
int root(int x);
void unite(int x, int y);

int main()
{
    init();
    
    int n, m;
    int x, y, z;

    scanf("%d %d", &n, &m);
    for (int i = 0; i < m; i++) {
        scanf("%d %d %d", &x, &y, &z);

        unite(x, y);
    }

    for (int i = 1; i <= n; i++) {
        int r = root(i);

        if (f[r] == 0) {
            f[r] = 1;
            ans++;
        }
    }

    printf("%d\n", ans);
    
    return 0;
}

void init(void)
{
    for (int i = 0; i < 100005; i++) {
        parent[i] = -1;
    }
}

int root(int x)
{
    if (parent[x] < 0) {
        return x;
    }

    return parent[x] = root(parent[x]);
}

void unite(int x, int y)
{
    x = root(x);
    y = root(y);

    if (x == y) return;

    parent[x] += parent[y];
    parent[y] = x;
}