a-a a-b a-c a-t aaa aab aac aao aap aar aat ab- aba abb abc abo abp abr abt ac- aca acb acc aco acp acr act aoa aob aoc aoo aop aor aot ap- apa apb apc apo app apr apt ar- ara arb arc aro arp arr art at- ata atb atc ato atp atr att b-p baa bab bac bao bap bar bat bba bbb bbc bbo bbp bbr bbt bca bcb bcc bco bcp bcr bct boa bob boc boo bop bor bot bpa bpb bpc bpo bpp bpr bpt bra brb bro brp brr brt bta btb btc bto btp btr btt c-- caa cab cac cao cap car cat cba cbb cbc cbo cbp cbr cbt cca ccb ccc cco ccp ccr cct co- coa cob coc coo cop cor cot cpa cpb cpc cpo cpp cpr cpt cra crb crc cro crp crr crt cta ctb ctc cto ctp ctr ctt oaa oab oac oao oap oar oat ob- oba obb obc obo obp obr obt oc- oca ocb occ oco ocp ocr oct oo- ooa oob ooc ooo oop oor oot op- opa opb opc opo opp opr opt or- ora orb orc oro orp orr ort ot- ota otb otc oto otp otr ott p-p paa pab pac pao pap par pat pba pbb pbc pbo pbp pbr pbt pca pcb pcc pco pcp pcr pct poa pob poc poo pop por pot ppa ppb ppc ppo ppp ppr ppt pra prb prc pro prp prr prt pt- pta ptb ptc pto ptp ptr ptt ra- raa rab rac rao rap rar rat rba rbb rbc rbo rbp rbr rbt rca rcb rcc rco rcp rcr rct roa rob roc roo rop ror rot rpa rpb rpc rpo rpp rpr rpt rra rrb rrc rrp rrr rrt rta rtb rtc rto rtp rtr rtt taa tab tac tao tap tar tat tba tbb tbc tbo tbp tbr tbt tca tcb tcc tco tcp tcr tct to- toa tob toc too top tor tot tpa tpb tpc tpo tpp tpr tpt tra trb trc tro trp trr trt tta ttb ttc tto ttp ttr ttt