a-a a-b a-t aaa aab aaf aao aap aar aat ab- aba abb abf abo abp abr abt af- afa afb aff afo afp afr aft aoa aob aof aoo aop aor aot ap- apa apb apf apo app apr apt ar- ara arb arf aro arp arr art at- ata atb atf ato atp atr att b-p baa bab baf bao bap bar bat bba bbb bbf bbo bbp bbr bbt bfa bfb bff bfo bfp bfr bft boa bob bof boo bop bor bot bpa bpb bpf bpo bpp bpr bpt bra brb brf bro brp brr brt bta btb btf bto btp btr btt faa fab faf fao fap far fat fba fbb fbf fbo fbp fbr fbt ffa fff ffo ffp ffr fft foa fob fof foo fop for fot fpa fpb fpo fpp fpr fpt fra frb frf fro frp frr frt fta ftb ftf fto ftp ftr ftt oaa oab oaf oao oap oar oat ob- oba obb obf obo obp obr obt of- ofa ofb off ofo ofp ofr oft oo- ooa oob oof ooo oop oor oot op- opa opb opf opo opp opr opt or- ora orb orf oro orp orr ort ot- ota otb otf oto otp otr ott p-p paa pab paf pao pap par pat pba pbb pbf pbo pbp pbr pbt pfa pfb pff pfo pfp pfr pft poa pob pof poo pop por pot ppa ppb ppf ppo ppp ppr ppt pra prb prf pro prp prr prt pt- pta ptb ptf pto ptp ptr ptt ra- raa rab raf rao rap rar rat rba rbb rbf rbo rbp rbr rbt rfa rfb rff rfo rfp rfr rft roa rob rof roo rop ror rot rpa rpb rpf rpo rpp rpr rpt rra rrb rrf rrp rrr rrt rta rtb rtf rto rtp rtr rtt taa tab taf tao tap tar tat tba tbb tbf tbo tbp tbr tbt tfa tfb tff tfo tfp tfr tft to- toa tob tof too top tor tot tpa tpb tpf tpo tpp tpr tpt tra trb trf tro trp trr trt tta ttb ttf tto ttp ttr ttt