import java.io.ByteArrayInputStream
import java.io.ByteArrayOutputStream
import java.io.PrintStream

fun main() = if (localEnv && execChecker) checker() else contest298b()

fun contest298b() = solve()

@OptIn(ExperimentalStdlibApi::class)
private fun solve() = Messiah_contest298b(MOD).exec {
    val (n, m) = readInt(2)
    val slimes = Array(n) { readInt() to readInt() }

    val uf = UnionFind(m + 1)
    var answer = 0

    val map = slimes.groupBy { it.second }.map { it.value.map { it.first }.distinct() }
    for (boxes in map) {
        for (i in 1..boxes.lastIndex) {
            if (uf.unite(boxes.first(), boxes[i])) answer++
        }
    }

    println(answer)
}

private class UnionFind(size: LongArray) {
    constructor(initSize: Int) : this(LongArray(initSize) { 1L })

    private val parent: IntArray = IntArray(size.size) { it }
    private val size: LongArray = size.copyOf()

    fun root(x: Int): Int {
        if (x == parent[x]) return x

        val xr = root(parent[x])
        parent[x] = xr
        return xr
    }

    fun unite(x: Int, y: Int): Boolean {
        val xr = root(x)
        val yr = root(y)
        if (xr == yr) return false
        if (size[xr] < size[yr]) return unite(yr, xr)
        size[xr] += size[yr]
        parent[yr] = xr
        return true
    }

    fun isSame(x: Int, y: Int): Boolean = root(x) == root(y)

    fun unite(pair: Pair<Int, Int>): Boolean = unite(pair.first, pair.second)
    fun isSame(pair: Pair<Int, Int>): Boolean = isSame(pair.first, pair.second)

    fun size(x: Int): Long = size[root(x)]
}

private const val MOD = 1_000_000_007

// region kokokara template dayo (^o^)
private const val execChecker = false
private val localEnv =
    runCatching { "ENABLE_DEBUG_MODE_FOR_COMPETITIVE_PROGRAMING" in System.getenv() }.getOrNull() ?: false

private fun checker() = Messiah_contest298b(MOD).exec {
    debugln("#######################################################")
    debugln("###############  executing check mode.  ###############")
    debugln("#######################################################")

    fun getOutPut(input: String, action: () -> Unit): String {
        System.setIn(ByteArrayInputStream(input.toByteArray()))
        val sysOut = ByteArrayOutputStream()
        System.setOut(PrintStream(sysOut))
        action()
        return sysOut.toString()
    }

    val wrongCases = mutableSetOf<List<String>>()

    while (wrongCases.size < 10) {
        /*
        examples
        val randomString = (1..20).map { ('a'..'z').random() }.joinToString("")
        val randomNum = Random.nextInt(0,2000)
         */
        val n = 0

        val input = buildString {
            appendln(n)
        }

        val solve = getOutPut(input, ::solve)
        val greedy = getOutPut(input, ::greedy)

        if (solve != greedy && wrongCases.add(listOf(solve, greedy))) {
            debugln("#################### wrong case: ${wrongCases.size} ####################")
            debugln("input:")
            debugln(input)
            debugln("solve:")
            debugln(solve)
            debugln("greedy:")
            debugln(greedy)
        }
    }
}

private fun greedy() = Messiah_contest298b(MOD).exec {
    TODO()
}

@Suppress("ClassName", "unused", "FunctionName", "PropertyName")
private class Messiah_contest298b(private val mod: Int) {
    //////////////////////////////////////////////////
    // IO
    //////////////////////////////////////////////////
    private val input = System.`in`
    private val buffer = ByteArray(1024)
    private var pointer = 0
    private var bufferLength = 0
    private val sb = StringBuilder()
    private fun Byte.isPrintable() = this in 33..126
    private fun Byte.isNumeric() = this in '0'.toByte()..'9'.toByte()
    private fun Byte.toNumVal() = if (this.isNumeric()) this - '0'.toByte() else error("$this is not numeric")
    private val lineSeparator: String = System.lineSeparator()

    private fun hasNextByte(): Boolean {
        return if (pointer < bufferLength) true else {
            pointer = 0
            bufferLength = input.read(buffer)
            bufferLength > 0
        }
    }

    private fun readByte(): Byte = if (hasNextByte()) buffer[pointer++] else -1
    private fun skipUnprintable() = run { while (hasNextByte() && !buffer[pointer].isPrintable()) pointer++ }
    private fun hasNext(): Boolean = run { skipUnprintable() }.run { hasNextByte() }
    private fun hasNextOrError() = if (!hasNext()) error("has no next element.") else Unit

    fun readString(): String {
        hasNextOrError()
        val sb = StringBuilder()
        var b = readByte()
        while (b.isPrintable()) {
            sb.appendCodePoint(b.toInt())
            b = readByte()
        }
        return sb.toString()
    }

    fun readLong(): Long {
        hasNextOrError()
        var n = 0L
        var negative = false
        var b = readByte()
        if (b == '-'.toByte()) {
            negative = true
            b = readByte()
        }
        if (!b.isNumeric()) error("$b is not numeric.")
        while (true) {
            when {
                b.isNumeric() -> n = n * 10 + b.toNumVal()
                b.toInt() == -1 || !b.isPrintable() -> return if (negative) -n else n
                else -> error("failed to parse. [n=$n, b=$b]")
            }
            b = readByte()
        }
    }

    fun readInt() = readLong()
        .let { if (it in Int.MIN_VALUE..Int.MAX_VALUE) it.toInt() else error("$it is not in range of Int.") }

    fun readIntAsIndex() = readInt().dec()

    fun readDouble(): Double {
        hasNextOrError()
        var n = 0.0
        var div = 1.0
        var negative = false
        var b = readByte()
        if (b == '-'.toByte()) {
            negative = true
            b = readByte()
        }
        do n = n * 10 + b.toNumVal()
        while (run { b = readByte() }.run { b.isNumeric() })
        if (b == '.'.toByte()) {
            while (run { b = readByte() }.run { b.isNumeric() })
                n += b.toNumVal() / (run { div *= 10 }.run { div })
        }
        return if (negative) -n else n
    }

    fun readString(size: Int): Array<String> = Array(size) { readString() }

    @Suppress("UNUSED_PARAMETER")
    fun readChars(h: Int, w: Int): Array<CharArray> = Array(h) { readString().toCharArray() }
    fun readLong(size: Int): LongArray = LongArray(size) { readLong() }
    fun readLong(h: Int, w: Int): Array<LongArray> = Array(h) { readLong(w) }
    fun readInt(size: Int): IntArray = IntArray(size) { readInt() }
    fun readInt(h: Int, w: Int): Array<IntArray> = Array(h) { readInt(w) }
    fun readIntAsIndex(size: Int): IntArray = IntArray(size) { readIntAsIndex() }
    fun readIntAsIndex(h: Int, w: Int): Array<IntArray> = Array(h) { readIntAsIndex(w) }
    fun readDouble(size: Int): DoubleArray = DoubleArray(size) { readDouble() }
    fun readDouble(h: Int, w: Int): Array<DoubleArray> = Array(h) { readDouble(w) }
    fun readBooleanWithSeparator(size: Int, trueElement: String): BooleanArray =
        BooleanArray(size) { readString() == trueElement }

    fun readBooleanWithSeparator(h: Int, w: Int, trueElement: String): Array<BooleanArray> =
        Array(h) { readBooleanWithSeparator(w, trueElement) }

    @Suppress("UNUSED_PARAMETER")
    fun readBooleanWithoutSeparator(size: Int, trueElement: Char): BooleanArray =
        readString().map { it == trueElement }.toBooleanArray()

    fun readBooleanWithoutSeparator(h: Int, w: Int, trueElement: Char): Array<BooleanArray> =
        Array(h) { readBooleanWithoutSeparator(w, trueElement) }

    fun println(): Unit = run { sb.append(lineSeparator) }
    fun print(any: Any): Unit = run { sb.append(any.toString()) }
    fun println(any: Any): Unit = run { sb.append(any.toString() + lineSeparator) }
    fun flush() = run { kotlin.io.println(sb); sb.clear() }
    fun debug(any: Any): Unit = run { if (localEnv) System.err.print(any) }
    fun debugln(any: Any): Unit = run { if (localEnv) System.err.println(any) }
    fun debugln(): Unit = run { if (localEnv) System.err.println() }
    fun debugExec(action: () -> Unit): Unit = run { if (localEnv) action() }

    fun exec(action: Messiah_contest298b.() -> Unit) {
        var t: Throwable? = null
        Thread(null, { action() }, "solve", 128 * 1024 * 1024)
            .apply { setUncaughtExceptionHandler { _, t1 -> t = t1 } }
            .apply { start() }.join()
        t?.let { throw it }
        kotlin.io.print(sb)
    }

    fun readLine(): Nothing = error("readLine is disabled.")

    //////////////////////////////////////////////////
    // MOD
    //////////////////////////////////////////////////
    fun Long.invertMod(): Long = invGcd(this).second

    fun Long.safeMod(): Long = (this % MOD).let { if (it < 0) it + MOD else it }

    fun Long.modPow(p: Long): Long {
        var x = this % MOD
        var y = p
        var result = 1L
        while (y > 0) {
            if (y % 2 == 1L) result = (result * x) % MOD
            y = y shr 1
            x = (x * x) % MOD
        }
        return result
    }

    fun Long.modPow(p: Long, m: Int): Long {
        var x = this % m
        var y = p
        var result = 1L
        while (y > 0) {
            if (y % 2 == 1L) result = (result * x) % m
            y = y shr 1
            x = (x * x) % m
        }
        return result
    }

    fun invGcd(a: Long): Pair<Long, Long> {
        val am = a.safeMod()
        if (a == 0L) return MOD.toLong() to 0L
        var s = MOD.toLong()
        var t = am
        var m0 = 0L
        var m1 = 1L
        while (t != 0L) {
            val u = s / t
            s -= t * u
            m0 -= m1 * u

            var temp = s
            s = t
            t = temp
            temp = m0
            m0 = m1
            m1 = temp
        }
        if (m0 < 0) m0 += MOD / s
        return s to m0
    }

    //////////////////////////////////////////////////
    // Misc
    //////////////////////////////////////////////////
    /**
     * `n.indices()` is sugar syntax of `0 until n`.
     */
    val Int.indices: IntRange get() = 0 until this

    /**
     * `[index] in [this]` is sugar syntax of `index in 0 until [this]`.
     */
    operator fun Int.contains(index: Int): Boolean = index in this.indices

    /**
     * `[this].mapIndices { transform }` is sugar syntax of `(0 until [this]).map{ transform(it) }`.
     */
    inline fun <R> Int.mapIndices(transform: (Int) -> R): List<R> = this.indices.map(transform)

    /**
     * `[this].mapIndices(x) { transform }` is sugar syntax of
     * `(0 until [this]).map{ y1-> (0 until [x]).map { x1-> transform(y1,x1) } }`.
     */
    inline fun <R> Int.mapIndices(x: Int, transform: (Int, Int) -> R): List<List<R>> =
        this.mapIndices { y1 -> x.mapIndices { x1 -> transform(y1, x1) } }

    /**
     * `[this].mapIndices(x) { transform }` is sugar syntax of
     * `(0 until [this]).map{ y1-> (0 until [x]).map { x1-> transform(y1,x1) } }`.
     */
    inline fun <R> Int.flatMapIndices(x: Int, transform: (Int, Int) -> R): List<R> =
        this.indices.flatMap { y1 -> x.mapIndices { x1 -> transform(y1, x1) } }

    /**
     * `[this].forEachIndices { transform }` is sugar syntax of `(0 until [this]).map{ transform(it) }`.
     */
    inline fun Int.forEachIndices(transform: (Int) -> Unit): Unit = this.indices.forEach(transform)

    /**
     * `[this].forEachIndices(x) { transform }` is sugar syntax of
     * `(0 until [this]).map{ y1-> (0 until [x]).map { x1-> transform(y1,x1) } }`.
     */
    inline fun Int.forEachIndices(x: Int, transform: (Int, Int) -> Unit): Unit =
        this.forEachIndices { y1 -> x.forEachIndices { x1 -> transform(y1, x1) } }

    /**
     * get characters numeric value.
     * e.g.: '0' to 0
     */
    fun Char.toNumericValue(): Int = this - '0'

    fun Char.caseToIndexedValue(): Int = this - 'a'

    fun String.toPoweredLong(p: Int): Long {
        check(this.isNotBlank())
        if (this[0] == '-') return -this.drop(1).toPoweredLong(p)
        var mulI = 1L
        repeat(p) { mulI *= 10 }
        val i = this.indexOf('.').takeIf { it != -1 } ?: return this.toLong() * mulI
        var mulD = 1L
        repeat(p - this.length + i + 1) { mulD *= 10 }
        return this.slice(0 until i).toLong() * mulI + this.slice(i + 1..this.lastIndex).toLong() * mulD
    }

    /**
     * make triple. e.g.:`1 to 2 to 3`
     */
    infix fun <A, B, C> Pair<A, B>.to(c: C): Triple<A, B, C> = Triple(this.first, this.second, c)

    fun YesNo(b: Boolean): String = if (b) Yes else No
    val Yes = "Yes"
    val No = "No"
    fun YES_NO(b: Boolean): String = if (b) YES else NO
    val YES = "YES"
    val NO = "NO"

    fun IntArray.swap(a: Int, b: Int): Unit = run { val temp = this[a]; this[a] = this[b]; this[b] = temp }
    fun LongArray.swap(a: Int, b: Int): Unit = run { val temp = this[a]; this[a] = this[b]; this[b] = temp }
    fun CharArray.swap(a: Int, b: Int): Unit = run { val temp = this[a]; this[a] = this[b]; this[b] = temp }
    fun <T> Array<T>.swap(a: Int, b: Int): Unit = run { val temp = this[a]; this[a] = this[b]; this[b] = temp }
    fun <T> MutableList<T>.swap(a: Int, b: Int): Unit = run { val temp = this[a]; this[a] = this[b]; this[b] = temp }

    fun IntArray.changeMinOf(i: Int, v: Int): Boolean = run { if (this[i] > v) run { this[i] = v; true } else false }
    fun IntArray.changeMaxOf(i: Int, v: Int): Boolean = run { if (this[i] < v) run { this[i] = v; true } else false }
    fun LongArray.changeMinOf(i: Int, v: Long): Boolean = run { if (this[i] > v) run { this[i] = v; true } else false }
    fun LongArray.changeMaxOf(i: Int, v: Long): Boolean = run { if (this[i] < v) run { this[i] = v; true } else false }
    fun Array<IntArray>.changeMinOf(i: Int, j: Int, v: Int): Boolean = run { this[i].changeMinOf(j, v) }
    fun Array<IntArray>.changeMaxOf(i: Int, j: Int, v: Int): Boolean = run { this[i].changeMaxOf(j, v) }
    fun Array<LongArray>.changeMinOf(i: Int, j: Int, v: Long): Boolean = run { this[i].changeMinOf(j, v) }
    fun Array<LongArray>.changeMaxOf(i: Int, j: Int, v: Long): Boolean = run { this[i].changeMaxOf(j, v) }

    /**
     * same usage as `IntArray.scan`, but it will faster than that.
     */
    inline fun IntArray.scanArray(initial: Int, operation: (acc: Int, Int) -> Int): IntArray {
        val accumulator = IntArray(this.size + 1).apply { this[0] = initial }
        for (i in this.indices) accumulator[i + 1] = operation(accumulator[i], this[i])
        return accumulator
    }

    /**
     * same usage as `LongArray.scan`, but it will faster than that.
     */
    inline fun LongArray.scanArray(initial: Long, operation: (acc: Long, Long) -> Long): LongArray {
        val accumulator = LongArray(this.size + 1).apply { this[0] = initial }
        for (i in this.indices) accumulator[i + 1] = operation(accumulator[i], this[i])
        return accumulator
    }

    /**
     * same usage as `IntArray.scanReduce`, but it will faster than that.
     */
    inline fun IntArray.scanReduceArray(operation: (acc: Int, Int) -> Int): IntArray {
        val accumulator = IntArray(this.size).apply { this[0] = this@scanReduceArray[0] }
        for (i in 1..this.lastIndex) accumulator[i] = operation(accumulator[i - 1], this[i])
        return accumulator
    }

    /**
     * same usage as `LongArray.scanReduce`, but it will faster than that.
     */
    inline fun LongArray.scanReduceArray(operation: (acc: Long, Long) -> Long): LongArray {
        val accumulator = LongArray(this.size).apply { this[0] = this@scanReduceArray[0] }
        for (i in 1..this.lastIndex) accumulator[i] = operation(accumulator[i - 1], this[i])
        return accumulator
    }
}
// endregion kokomade template dayo (^o^)