import java.util.Stack

object Postfix {

  var current = new Stack[Int]()

  def calculate(post: List[String]): Int = {
    if (post.isEmpty) current.pop()
    else {
      post.head match {
        case "+" => {
          val top = current.pop()
          val next = current.pop()
          current.push(top + next)
        }
        case "-" => {
          val top = current.pop()
          val next = current.pop()
          current.push(next - top)
        }
        case "*" => {
          val top = current.pop()
          val next = current.pop()
          current.push(top * next)
        }
        case i => current.push(i.toInt)
      }
      calculate(post.tail)
    }
  }
}

object Main extends App {

  val post = scala.io.StdIn.readLine()
  //println(post.toString().split(" ").toList)
  println(Postfix.calculate(post.toString().split(" ").toList))
}