NParserError@(1:5-1:6)='3'
Nodes[Node]
  f_0
    e_1
      '1'@(1:1-1:2)
      e_1
        '1'@(1:2-1:3)
        e_0
          '0'@(1:3-1:4)
        y_0
          x
            '2'@(1:4-1:5)
      y_1
  '3'@(1:5-1:6)