a-a a-b aaa aab aad aap aar ab- aba abb abd abp abr ad- ada adb add adp adr ap- apa apb apd app apr ar- ara arb ard arp arr b-p baa bab bad bap bar bba bbb bbd bbp bbr bda bdb bdd bdp bdr bpa bpb bpd bpp bpr bra brb brd brp brr daa dab dad dap dar dba dbb dbd dbp dbr dda ddb ddd ddp ddr dpa dpb dpd dpp dpr dra drb drd drp drr p-p paa pab pad pap par pba pbb pbd pbp pbr pda pdb pdd pdp pdr ppa ppb ppd ppp ppr pra prb prd prp prr ra- raa rab rad rap rar rba rbb rbd rbp rbr rda rdb rdd rdp rdr rpa rpb rpd rpp rpr rra rrb rrd rrp rrr