    # File lib/nokogiri/css/parser.rb, line 532
    def _reduce_40(val, _values, result)
                   # n+3, -n+3
            if val[0] == 'n'
              val.unshift("1")
              result = Node.new(:AN_PLUS_B, val)
            elsif val[0] == '-n'
              val[0] = 'n'
              val.unshift("-1")
              result = Node.new(:AN_PLUS_B, val)
            else
              raise Racc::ParseError, "parse error on IDENT '#{val[1]}'"
            end

        result
    end