import scala.io.StdIn._

object Main {
    def main(args: Array[String]){
        val r = readLine.split(" ").map(_.toInt)
        val n = readLine.toInt
        
        val q = r(0)
        val h = min(q * 2, r(1))
        val s = min(h * 2, r(2))
        val d = min(s * 2, r(3))
        
        val _d = n / 2
        val _s = (n % 2)
        
        printf("%s\n", _d * d + _s * s)
    }
    
    def min(a: Long, b: Long): Long = {
        if (a > b) {
            b
        } else {
            a
        }
    }
}