arr = gets.chomp.split
stack = []

arr.each{|c|
	case c
	when "+"
		stack.push(stack.pop + stack.pop)
	when "-"
		stack.push(- stack.pop + stack.pop)
	when "*"
		stack.push(stack.pop * stack.pop)
	else
		stack.push(c.to_i)
	end
}
puts stack[0]