Решение

import java.io.BufferedReader
import java.io.InputStreamReader
import java.io.BufferedWriter
import java.io.OutputStreamWriter
import java.util.PriorityQueue

fun main() {
    val reader = BufferedReader(InputStreamReader(System.`in`))
    val writer = BufferedWriter(OutputStreamWriter(System.out))

    val n = reader.readLine().toInt()
    val numbers = reader.readLine().trim().split("\\\\s+".toRegex()).map { it.toLong() }

    val pq = PriorityQueue<Long>()
    pq.addAll(numbers)

    var totalCost = 0.0

    while (pq.size > 1) {
        val a = pq.poll()
        val b = pq.poll()
        val sum = a + b
        totalCost += sum * 0.05
        pq.add(sum)
    }

    writer.write("%.2f".format(totalCost))
    writer.newLine()

    reader.close()
    writer.close()
}