hackerrank easy puzzle

PickingNumbers.kt

import java.io.FileInputStream
import java.util.*

// https://www.hackerrank.com/challenges/picking-numbers/problem

// Complete the pickingNumbers function below.
fun pickingNumbers(a: Array<Int>): Int {
    val counts = a.groupingBy{ it }.eachCount()
    val entries = counts.entries.asSequence().sortedBy { e -> e.key }.toList()
    var maxLen = 0
    for (i in 1 until entries.size) {
        maxLen = Math.max(maxLen, entries[i].value)
        if (entries[i].key - entries[i-1].key <= 1) {
            val len = entries[i].value + entries[i-1].value
            maxLen = Math.max(maxLen, len)
        }
    }
    return maxLen
}

fun main(args: Array<String>) {
    FileInputStream(args[0]).use { stream ->
        val scan = Scanner(stream)
        val n = scan.nextLine()
        val a = scan.nextLine().split(" ").map{ it.trim().toInt() }.toTypedArray()
        val result = pickingNumbers(a)
        println(result)
    }
}