import java.util.*

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val t = listOf(sc.nextLong() * 8, sc.nextLong() * 4, sc.nextLong() * 2, sc.nextLong())
    val n = sc.nextLong()

    if (n % 2 == 0L) {
        println(n / 2 * t.min()!!)
    } else {
        println(n / 2 * t.min()!! + t.subList(0, 3).min()!! / 2)
    }
}