class Calc0049
  def initialize(args)
    args = args.map { |l| l.chomp.split(/\s+/) }
    @s = args.shift.first
  end

  def run
    stack = []
    @s.scan(/\d+|[+*]/).each do |t|
      case t
      when /\d+/
        t = t.to_i
        if stack.empty?
          stack.push(t)
        else
          op = stack.pop
          target = stack.pop
          case op
          when '+'
            stack.push(target * t)
          when '*'
            stack.push(target + t)
          end
        end
      when '+', '*'
        stack.push(t)
      end
    end
    stack.pop
  end
end

puts Calc0049.new(STDIN.readlines).run if __FILE__ == $0