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 Kotlin (1.3.71) (judge verdict: Accepted)


typealias Graph = MutableList<MutableList<Int>>
fun create_empty_graph(n:Int):Graph{
    return MutableList(n) {_ -> mutableListOf<Int>()}
}
fun main(args:Array<String>) {
    val (n,m) = readLine()!!.split(" ").map(String::toInt)
    var g = create_empty_graph(n)
    for (_i in 0 until m) {
        var (x,y,_) = readLine()!!.split(" ").map(String::toInt)
        x--
        y--
        g[x].add(y)
        g[y].add(x)
    }

    var used = MutableList(n) {_ -> false}
    var cnt = 0
    for (i in 0 until n) {
        if(used[i]) continue
        var stack = mutableListOf<Int>()
        cnt++
        used[i] = true
        stack.add(i)
        while(!stack.isEmpty()){
            val v = stack.lastOrNull()!!
            stack.removeAt(stack.size-1)
            for(to in g[v]) {
                if(!used[to]) {
                    used[to] = true
                    stack.add(to)
                }
            }
        }
    }

    println(cnt)
}