b-p bbb bbi bbo bbp bbr bbs bi- bib bii bio bip bir bis bob boi boo bop bor bos bpb bpi bpo bpp bpr bps brb bri bro brp brr brs bsb bsi bso bsp bsr bss ibb ibi ibo ibp ibr ibs iib iii iio iip iir iis io- iob ioi ioo iop ior ios ipb ipi ipo ipp ipr ips ir- irb iri iro irp irr irs is- isb isi iso isp isr iss o-i ob- obb obi obo obp obr obs oib oii oio oip oir ois oo- oob ooi ooo oop oor oos op- opb opi opo opp opr ops or- orb ori oro orp orr ors os- osb osi oso osp osr oss p-p pbb pbi pbo pbp pbr pbs pib pii pio pip pir pis pob poi poo pop por pos ppb ppi ppo ppp ppr pps prb pri pro prp prr prs ps- psb psi pso psp psr pss rbb rbi rbo rbp rbr rbs rib rii rio rip rir ris rob roi roo rop ror ros rpb rpi rpo rpp rpr rps rrb rri rrp rrr rrs rsb rsi rso rsp rsr rss sbb sbi sbo sbp sbr sbs sib sii sio sip sir sis sob soi soo sop sor sos spb spi spo spp spr sps sr- srb sri sro srp srr srs ss- ssb ssi sso ssp ssr sss