import java.util.* fun main() { val sc = Scanner(System.`in`) val n = sc.nextInt() val m = sc.nextInt() val slimes = List(n) { Pair(sc.nextInt() - 1, sc.nextInt() - 1) } // val (n, m) = readLine()!!.split(" ").map { it.toInt() } // val slimes = mutableListOf>() // for (i in 0 until n) { // val (b, c) = readLine()!!.split(" ").map { it.toInt() } // slimes.add(Pair(b - 1, c - 1)) // } val dsu = DSU(m) val color_leaders = MutableList(n) { -1 } var ans = 0 for ((box, color) in slimes) { if (color_leaders[color] == -1) { color_leaders[color] = box } else { if (!dsu.same(box, color_leaders[color])) { dsu.merge(box, color_leaders[color]) ans += 1 } } } println(ans) } fun eprintln(obj: Any) = System.err.println(obj.toString()) /** * Disjoint set union. * * convert from [AtCoderLibraryForJava - DSU](https://github.com/NASU41/AtCoderLibraryForJava/blob/8b3a3b599790a9ca8c7dd92e036af4ddc5be1b05/DSU/DSU.java) */ class DSU(private val n: Int) { private val parentOrSize: IntArray = IntArray(n) { -1 } /** * Merge nodes. */ fun merge(a: Int, b: Int): Int { if (a !in 0 until n) throw IndexOutOfBoundsException("a=$a") if (b !in 0 until n) throw IndexOutOfBoundsException("b=$b") var x = leader(a) var y = leader(b) if (x == y) return x if (-parentOrSize[x] < -parentOrSize[y]) { val tmp = x x = y y = tmp } parentOrSize[x] += parentOrSize[y] parentOrSize[y] = x return x } /** * True if two nodes are connected. */ fun same(a: Int, b: Int): Boolean { if (a !in 0 until n) throw IndexOutOfBoundsException("a=$a") if (b !in 0 until n) throw IndexOutOfBoundsException("b=$b") return leader(a) == leader(b) } /** * Get its leader node. */ fun leader(a: Int): Int { return if (parentOrSize[a] < 0) { a } else { parentOrSize[a] = leader(parentOrSize[a]) parentOrSize[a] } } /** * A group's size. */ fun size(a: Int): Int { if (a !in 0 until n) throw IndexOutOfBoundsException("" + a) return -parentOrSize[leader(a)] } /** * Group by leader. */ fun groups(): ArrayList> { val leaderBuf = IntArray(n) val groupSize = IntArray(n) for (i in 0 until n) { leaderBuf[i] = leader(i) groupSize[leaderBuf[i]]++ } val result = ArrayList>(n) for (i in 0 until n) { result.add(ArrayList(groupSize[i])) } for (i in 0 until n) { result[leaderBuf[i]].add(i) } result.removeIf { it.isEmpty() } return result } }