object Solution {
    def groupByDiff(acc: List[Vector[Int]], n: Int): List[Vector[Int]] = {
        val lastVec = acc.head
        val last = lastVec.headOption.getOrElse(n - 2)
        if (n - last <= 1) (lastVec :+ n) :: acc.drop(1) else Vector(n) :: acc
    }
/*    
    def main(args: Array[String]) {
        val n = readLine()
        val xs = readLine().split(" ").toVector.map(_.toInt).sorted
        val pairs = for {
            i <- (0 until xs.length)
            j <- (i + 1 until xs.length)
            r = Math.abs(xs(i) - xs(j))
            if r <= 1
        } yield ((xs(i), xs(j)))
        println(pairs)
        val sortedPairs = pairs.map(_._1).sorted
        val grouped = sortedPairs.groupBy(p => p).mapValues(_.size).map {case (k, v) => v}
        println(grouped)
        val res = grouped.max
        println(res)
    }
*/
    def main(args: Array[String]) {
        val n = readLine()
        val xs = readLine().split(" ").toList.map(_.toInt).sorted
        val init = List(Vector[Int]())
        val res = xs.foldLeft(init)(groupByDiff)
        println(res.map(_.length).max)
    }
}