19 rules
rule 1: valid
rule 2: valid
rule 3: valid
rule 4: valid
rule 5: valid
rule 6: valid
rule 7: valid
rule 8: valid
rule 9: valid
rule 10: valid
rule 11: valid
rule 12: valid
rule 13: valid
rule 14: valid
rule 15: valid
rule 16: valid
rule 17: valid
rule 18: valid
rule 19: valid