U12 tt s length L U23 tt cons N zeros cons 0 U11 tt U12 tt U21 tt U22 tt U22 tt U23 tt length nil 0 length cons N U11 tt take 0 IL nil take s M cons N U21 tt U12 1 tt 0 s 1 length 1 U23 1 cons 1 zeros 0 0 0 U11 1 U21 1 U22 1 nil 0 take 2 FULL ./TRS/TRCSR/OvConsOS_nosorts-noand_L.trs