-er a-a a-b aaa aab aae aap aar ab- aba abb abe abp abr aea aeb aee aep aer ap- apa apb ape app apr ar- ara arb are arp arr b-p baa bab bae bap bar bba bbb bbe bbp bbr be- bea beb bee bep ber bpa bpb bpe bpp bpr bra brb bre brp brr eaa eab eae eap ear eba ebb ebe ebp ebr eea eeb eee eep eer ep- epa epb epe epp epr era erb ere erp err p-p paa pab pae pap par pba pbb pbe pbp pbr pea peb pee pep per ppa ppb ppe ppp ppr pra prb pre prp prr ra- raa rab rae rap rar rba rbb rbe rbp rbr re- rea reb ree rep rer rpa rpb rpe rpp rpr rra rrb rrp rrr