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: Runtime Error)

#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>
#include <stdlib.h>
#include <string.h>

static unsigned N, M;
static uint8_t *V;
static unsigned *L;
static _Bool *visited;

static
void dfs(const unsigned n)
{
    for (unsigned i = 0; i < L[n]; i ++) {
        if (!visited[V[M*n + i]]) {
            visited[V[M*n + i]] = 1;
            dfs(V[M*n+i]);
        }
    }
}

int main(void)
{
    scanf("%u %u", &N, &M);

    V = malloc(sizeof(*V) * M * N);
    L = malloc(sizeof(*L) * N);
    memset(L, 0, sizeof(*L) * N);
    visited = malloc(sizeof(*visited) * N);
    memset(visited, 0, sizeof(*visited) * N);

    for (unsigned i = 0; i < M; i ++) {
        unsigned x, y, z;
        scanf("%u %u %u", &x, &y, &z);
        --x; --y;
        V[M*x + L[x]] = y;
        V[M*y + L[y]] = x;
        L[x]++;
        L[y]++;
    }

    uint64_t cnt = 0;
    for (unsigned n = 0; n < N; n ++) {
        if (!visited[n]) {
            visited[n] = 1;
            cnt++;
            dfs(n);
        }
    }

    printf("%" PRIu64 "\n", cnt);

    return 0;
}