Help Mocha - KOTLIN

package com.company

import java.util.*


private const val N = 300000

fun main() {
    val sc = Scanner(System.`in`)
    val d = sc.nextInt()
    val result = helpMocha(d)
    println(result)
}

var isPrime = BooleanArray(N + 1)
var primes = ArrayList<Long>()

fun sieve() {
    for (i in 2..N) {
        if (isPrime[i]) {
            var j = (i * i).toLong()
            while (j <= N) {
                isPrime[j.toInt()] = false
                j += i
            }
            primes.add(i.toLong())
        }
    }
}

fun lowerBound(list: ArrayList<Long>, x: Long): Long {
    val n = list.size
    var lo = 0
    var hi = n - 1
    var res = n - 1
    while (lo <= hi) {
        val mid = lo + (hi - lo) / 2
        if (list[mid] == x)
            return x
        else if (list[mid] > x) {
            res = mid
            hi = mid - 1
        } else {
            lo = mid + 1
        }
    }
    return list[res]
}


fun helpMocha(d: Int): Long {
    Arrays.fill(isPrime, true)
    sieve()
    val a = lowerBound(primes, (1 + d).toLong())
    val b = lowerBound(primes, a + d)
    return a * b
}