-er a-a a-b aaa aab aae aao aap aar aas aax ab- aba abb abe abo abp abr abs abx aea aeb aee aeo aep aer aes aex aoa aob aoe aoo aop aor aos aox ap- apa apb ape apo app apr aps apx ar- ara arb are aro arp arr ars arx as- asa asb ase aso asp asr ass asx ax- axa axe axo axp axr axs axx b-p baa bab bae bao bap bar bas bax bba bbb bbe bbo bbp bbr bbs bbx be- bea beb bee beo bep ber bes bex boa bob boe boo bop bor bos box bpa bpb bpe bpo bpp bpr bps bpx bra brb bre bro brp brr brs brx bsa bsb bse bso bsp bsr bss bsx bxb bxo bxx eaa eab eae eao eap ear eas eax eba ebb ebe ebo ebp ebr ebs ebx eea eeb eee eeo eep eer ees eex eo- eoa eob eoe eoo eop eor eos ep- epa epb epe epo epp epr eps epx era erb ere ero erp err ers es- esa esb ese eso esp esr ess esx ex- exa exe exo exp exr exs exx oaa oab oae oao oap oar oas oax ob- oba obb obe obo obp obr obs obx oea oeb oee oeo oep oer oes oex oo- ooa oob ooo oop oor oos oox op- opa opb ope opo opp opr ops opx or- ora orb ore oro orp orr ors orx os- osa osb ose oso osp osr oss osx ox- oxa oxb oxo oxx p-p paa pab pae pao pap par pas pax pba pbb pbe pbo pbp pbr pbs pbx pea peb pee peo pep per pes pex poa pob poe poo pop por pos pox ppa ppb ppe ppo ppp ppr pps ppx pra prb pre pro prp prr prs prx ps- psa psb pse pso psp psr pss psx pxe pxr pxs ra- raa rab rae rao rap rar ras rax rba rbb rbe rbo rbp rbr rbs rbx re- rea reb ree reo rep rer res rex roa rob roe roo rop ror ros rox rpa rpb rpe rpo rpp rpr rps rpx rra rrb rrp rrr rrs rsa rsb rse rso rsp rsr rss rsx rxp rxr rxs saa sab sae sao sap sar sas sax sba sbb sbe sbo sbp sbr sbs sbx se- sea seb see seo sep ser ses sex soa sob soe soo sop sor sos sox spa spb spe spo spp spr sps spx sr- sra srb sre sro srp srr srs srx ss- ssa ssb sse sso ssp ssr sss ssx sxs xaa xap xar xas xbe xbr xbx xee xep xer xes xex xoa xoo xop xor xos xox xpa xpb xpe xpo xpp xps xrx xsa xsb xsp xss xxo xxp xxx