import java.util.Scanner import scala.collection.Searching._ import scala.annotation.tailrec import scala.collection.immutable.{NumericRange, Queue} import scala.collection.mutable import scala.io.StdIn.readLine class IUnionFind(val size: Int) { private case class Node(var parent: Option[Int], var treeSize: Int) private val nodes = Array.fill[Node](size)(new Node(None, 1)) def union(t1: Int, t2: Int): IUnionFind = { if (t1 == t2) return this val root1 = root(t1) val root2 = root(t2) if (root1 == root2) return this val node1 = nodes(root1) val node2 = nodes(root2) if (node1.treeSize < node2.treeSize) { node1.parent = Some(t2) node2.treeSize += node1.treeSize } else { node2.parent = Some(t1) node1.treeSize += node2.treeSize } this } def connected(t1: Int, t2: Int): Boolean = t1 == t2 || root(t1) == root(t2) def root(t: Int): Int = nodes(t).parent match { case None => t case Some(p) => root(p) } } object Main { def solve(sc: => Scanner): Unit = { val A = Array.fill(sc.nextInt)(sc.nextLong) println(if (A.toSet.size != A.size) ("NO") else { val B = A.sorted var flag = true for (i <- Range(1, B.size)) { if (B(1) - B(0) != B(i) - B(i - 1)) (flag = false) } if (flag) ("YES") else ("NO") }) } def gcd(i: Long, j: Long): Long = { if (i < j) (gcd(j, i)) else (if (j == 0) (i) else (gcd(j, i % j))) } def main(args: Array[String]): Unit = { val sc: Scanner = new Scanner(System.in) solve(sc) } }