Updated production rules:
rule_1: A1 -> A20 A18 18 A10 A17 15 A15 A2
rule_2: A2 -> 14 A4 4 A3 1
rule_61: A18 -> 19 A10 A19
rule_63: A19 -> 10 17
rule_64: A20 -> A4 6 4 A21