a-a a-b a-i a-t aaa aab aai aap aar aat ab- aba abb abi abp abr abt ai- aia aib aii aip air ait ap- apa apb api app apr apt ar- ara arb ari arp arr art at- ata atb ati atp atr att b-p baa bab bai bap bar bat bba bbb bbi bbp bbr bbt bi- bia bib bii bip bir bit bpa bpb bpi bpp bpr bpt bra brb bri brp brr brt bta btb bti btp btr btt ia- iaa iab iai iap iar iat iba ibb ibi ibp ibr ibt iia iib iii iip iir iit ipa ipb ipi ipp ipr ipt ir- ira irb iri irp irr irt ita itb iti itp itt p-p paa pab pai pap par pat pba pbb pbi pbp pbr pbt pia pib pii pip pir pit ppa ppb ppi ppp ppr ppt pra prb pri prp prr prt pt- pta ptb pti ptp ptr ptt ra- raa rab rai rap rar rat rba rbb rbi rbp rbr rbt ria rib rii rip rir rit rpa rpb rpi rpp rpr rpt rra rrb rri rrp rrr rrt rta rtb rti rtp rtr rtt taa tab tai tap tar tat tba tbb tbi tbp tbr tbt tia tib tii tip tir tit tpa tpb tpi tpp tpr tpt tra trb tri trp trr trt tta ttb tti ttp ttr ttt