b-p bbb bbi bbo bbp bbs bbt bi- bib bii bio bip bis bit bob boi boo bop bos bot bpb bpi bpo bpp bps bpt bsb bsi bso bsp bss bst btb bti bto btp bts btt ibb ibi ibo ibp ibs ibt iib iii iio iip iis iit io- iob ioi ioo iop ios iot ipb ipi ipo ipp ips ipt is- isb isi iso isp iss ist itb iti ito itp its itt o-i ob- obb obi obo obp obs obt oib oii oio oip ois oit oo- oob ooi ooo oop oos oot op- opb opi opo opp ops opt os- osb osi oso osp oss ost ot- otb oti oto otp ots ott p-p pbb pbi pbo pbp pbs pbt pib pii pio pip pis pit pob poi poo pop pos pot ppb ppi ppo ppp pps ppt ps- psb psi pso psp pss pst pt- ptb pti pto ptp pts ptt sbb sbi sbo sbp sbs sbt sib sii sio sip sis sit sob soi soo sop sos sot spb spi spo spp sps spt ss- ssb ssi sso ssp sss sst stb sti sto stp sts stt tbb tbi tbo tbp tbs tbt tib tii tio tip tis tit to- tob toi too top tos tot tpb tpi tpo tpp tps tpt tsb tsi tso tsp tss tst ttb tti tto ttp tts ttt