import scala.collection.mutable.Stack

val lst = io.StdIn.readLine.split(" ")

val num = "\\d+".r

// println(lst.toList)

val stack = new Stack[Int]

lst map {
  case "+" =>
    val lft = stack.pop
    val rgt = stack.pop
    stack push rgt + lft
  case "-" =>
    val lft = stack.pop
    val rgt = stack.pop
    stack push rgt - lft
  case "*" =>
    val lft = stack.pop
    val rgt = stack.pop
    stack push rgt * lft
  case other => stack push other.toInt
}

println(stack.pop)

