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 (1.0.0) (judge verdict: Accepted)

import java.io.IOException
import java.io.InputStream
import java.io.PrintWriter
import java.util.NoSuchElementException

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val n = sc.nextInt()
    val m = sc.nextInt()
    val uf = UnionFind(n)
    repeat(m) {
        val x = sc.nextInt() - 1
        val y = sc.nextInt() - 1
        sc.nextInt()
        uf.unite(x, y)
    }
    println((0 until n).map { uf.find(it) }.distinct().size)
}

class UnionFind(n: Int) {

    private val parent = IntArray(n) { it }
    private val rank = IntArray(n)

    fun find(x: Int): Int =
            if (parent[x] == x) x else {
                parent[x] = find(parent[x])
                parent[x]
            }

    fun unite(x: Int, y: Int) {
        val px = find(x)
        val py = find(y)
        if (px == py) return
        if (rank[px] < rank[py]) {
            parent[px] = py
        } else {
            parent[py] = px
            if (rank[px] == rank[py]) rank[px]++
        }
    }

    fun same(x: Int, y: Int): Boolean = find(x) == find(y)

    fun size(x: Int): Int = rank[find(x)]

}

class Scanner(private val `in`: InputStream) {
    private val buffer = ByteArray(1024)
    private var ptr = 0
    private var buflen = 0

    companion object {
        private fun isPrintableChar(b: Byte): Boolean = b in 33..126
        private fun isNumericChar(b: Byte): Boolean = b in 48..57
        private fun digit(b: Byte): Int = b - 48
    }

    fun hasNextByte(): Boolean {
        if (ptr < buflen) return true
        ptr = 0
        try {
            buflen = `in`.read(buffer)
        } catch (e: IOException) {
            e.printStackTrace()
        }
        return 0 < buflen
    }

    private fun readByte(): Byte = if (hasNextByte()) buffer[ptr++] else -1

    private fun skipUnprintable() {
        while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++
    }

    fun hasNext(): Boolean {
        skipUnprintable()
        return hasNextByte()
    }

    fun next(): String {
        if (!hasNext()) throw NoSuchElementException()
        return buildString {
            var b = readByte()
            while (isPrintableChar(b)) {
                appendCodePoint(b.toInt())
                b = readByte()
            }
        }
    }

    fun nextInt(): Int {
        if (!hasNext()) throw NoSuchElementException()
        var n = 0
        var b = readByte()
        val minus = b.toChar() == '-'
        if (minus) b = readByte()
        if (!isNumericChar(b)) throw NumberFormatException()
        do {
            n *= 10
            n += digit(b)
            b = readByte()
        } while (isNumericChar(b))
        return if (minus) -n else n
    }

    fun nextInts(n: Int): Array<Int> = Array(n) { nextInt() }

    fun nextIntArray(n: Int): IntArray = IntArray(n) { nextInt() }

    fun nextIntArrays(n: Int, m: Int): Array<IntArray> {
        val arrays = Array(m) { IntArray(n) }
        repeat(n) { i -> repeat(m) { j -> arrays[j][i] = nextInt() } }
        return arrays
    }

    fun nextLong(): Long {
        if (!hasNext()) throw NoSuchElementException()
        var n = 0L
        var b = readByte()
        val minus = b.toChar() == '-'
        if (minus) b = readByte()
        if (!isNumericChar(b)) throw NumberFormatException()
        do {
            n *= 10
            n += digit(b)
            b = readByte()
        } while (isNumericChar(b))
        return if (minus) -n else n
    }

    fun nextLongs(n: Int): Array<Long> = Array(n) { nextLong() }

    fun nextLongArray(n: Int): LongArray = LongArray(n) { nextLong() }

    fun nextLongArrays(n: Int, m: Int): Array<LongArray> {
        val arrays = Array(m) { LongArray(n) }
        repeat(n) { i -> repeat(m) { j -> arrays[j][i] = nextLong() } }
        return arrays
    }

}