class Calcparser
rule
  target: exp { print val[0] }

  exp: exp '+' exp
     | exp '*' exp
     | '(' exp ')'
     | NUMBER

---- inner

  def parse
    @q = STDIN.read.split(' ')
    do_parse
  end

  def next_token
    a = @q.shift
    begin
      b = Integer(a)
      return [:NUMBER, b]
    rescue
      return [a,a]
    end
  end
---- footer

Calcparser.new.parse