-er a-a a-b aaa aab aae aap aar aas ab- aba abb abe abp abr abs aea aeb aee aep aer aes ap- apa apb ape app apr aps ar- ara arb are arp arr ars as- asa asb ase asp asr ass b-p baa bab bae bap bar bas bba bbb bbe bbp bbr bbs be- bea beb bee bep ber bes bpa bpb bpe bpp bpr bps bra brb bre brp brr brs bsa bsb bse bsp bsr bss eaa eab eae eap ear eas eba ebb ebe ebp ebr ebs eea eeb eee eep eer ees ep- epa epb epe epp epr eps era erb ere erp err ers es- esa esb ese esp esr ess p-p paa pab pae pap par pas pba pbb pbe pbp pbr pbs pea peb pee pep per pes ppa ppb ppe ppp ppr pps pra prb pre prp prr prs ps- psa psb pse psp psr pss ra- raa rab rae rap rar ras rba rbb rbe rbp rbr rbs re- rea reb ree rep rer res rpa rpb rpe rpp rpr rps rra rrb rrp rrr rrs rsa rsb rse rsp rsr rss saa sab sae sap sar sas sba sbb sbe sbp sbr sbs se- sea seb see sep ser ses spa spb spe spp spr sps sr- sra srb sre srp srr srs ss- ssa ssb sse ssp ssr sss