-er a-a a-b a-t aaa aab aae aap aar aat ab- aba abb abe abp abr abt aea aeb aee aep aer aet ap- apa apb ape app apr apt ar- ara arb are arp arr art at- ata atb ate atp atr att b-p baa bab bae bap bar bat bba bbb bbe bbp bbr bbt be- bea beb bee bep ber bet bpa bpb bpe bpp bpr bpt bra brb bre brp brr brt bta btb bte btp btr btt eaa eab eae eap ear eat eba ebb ebe ebp ebr ebt eea eeb eee eep eer eet ep- epa epb epe epp epr ept era erb ere erp err ert eta etb ete etp etr ett p-p paa pab pae pap par pat pba pbb pbe pbp pbr pbt pea peb pee pep per pet ppa ppb ppe ppp ppr ppt pra prb pre prp prr prt pt- pta ptb pte ptp ptr ptt ra- raa rab rae rap rar rat rba rbb rbe rbp rbr rbt re- rea reb ree rep rer ret rpa rpb rpe rpp rpr rpt rra rrb rrp rrr rrt rta rtb rte rtp rtr rtt taa tab tae tap tar tat tba tbb tbe tbp tbr tbt te- tea teb tee tep ter tet tpa tpb tpe tpp tpr tpt tra trb tre trp trr trt tta ttb tte ttp ttr ttt