hall("entry","2")
hall("2","4")
hall("2","3")
hall("2","9")
hall("3","4")
hall("3","5")
hall("3","6")
hall("3","7")
hall("3","9")
hall("4","8")
hall("4","9")
hall("5","15")
hall("5","19")
hall("6","7")
hall("6","15")
hall("7","9")
hall("7","10")
hall("7","11")
hall("7","12")
hall("7", "15")
hall("8","14")
hall("9","10")
hall("9","14")
hall("10","11")
hall("11","12")
hall("11","13")
hall("11","16")
hall("11","17")
hall("12","15")
hall("13","16")
hall("16","17")
hall("17","exit")
avoid(["10","12"])