-er a-a a-b a-i aaa aab aae aai aao aar aas aax ab- aba abb abe abi abo abr abs abx aea aeb aee aei aeo aer aes aex ai- aia aib aie aii aio air ais aix aoa aob aoe aoi aoo aor aos aox ar- ara arb are ari aro arr ars arx as- asa asb ase asi aso asr ass asx ax- axa axe axi axo axr axs axx baa bab bae bai bao bar bas bax bba bbb bbe bbi bbo bbr bbs bbx be- bea beb bee bei beo ber bes bex bi- bia bib bie bii bio bir bis bix boa bob boe boi boo bor bos box bra brb bre bri bro brr brs brx bsa bsb bse bsi bso bsr bss bsx bxb bxi bxo bxx eaa eab eae eai eao ear eas eax eba ebb ebe ebi ebo ebr ebs ebx eea eeb eee eeo eer ees eex eia eib eie eii eio eir eis eix eo- eoa eob eoe eoi eoo eor eos era erb ere eri ero err ers es- esa esb ese esi eso esr ess esx ex- exa exe exi exo exr exs exx ia- iaa iab iae iai iao iar ias iba ibb ibe ibi ibo ibr ibs ibx ie- iea iee iei ier ies iex iia iib iie iii iio iir iis iix io- ioa iob ioe ioi ioo ior ios ir- ira irb ire iri iro irr irs irx is- isa isb ise isi iso isr iss ixe ixi o-i oaa oab oae oai oao oar oas oax ob- oba obb obe obi obo obr obs obx oea oeb oee oei oeo oer oes oex oia oib oie oii oio oir ois oo- ooa oob ooi ooo oor oos oox or- ora orb ore ori oro orr ors orx os- osa osb ose osi oso osr oss osx ox- oxa oxb oxi oxo oxx ra- raa rab rae rai rao rar ras rax rba rbb rbe rbi rbo rbr rbs rbx re- rea reb ree rei reo rer res rex ria rib rie rii rio rir ris rix roa rob roe roi roo ror ros rox rra rrb rri rrr rrs rsa rsb rse rsi rso rsr rss rsx rxr rxs saa sab sae sai sao sar sas sax sba sbb sbe sbi sbo sbr sbs sbx se- sea seb see sei seo ser ses sex sia sib sie sii sio sir sis six soa sob soe soi soo sor sos sox sr- sra srb sre sri sro srr srs srx ss- ssa ssb sse ssi sso ssr sss ssx sxi sxs xaa xar xas xbe xbr xbx xee xer xes xex xia xie xii xio xis xix xoa xoi xoo xor xos xox xrx xsa xsb xsi xss xxi xxo xxx