-ic bbb bbc bbi bbo bbr bbt bcb bcc bci bco bcr bct bi- bib bic bii bio bir bit bob boc boi boo bor bot brb bri bro brr brt btb btc bti bto btr btt c-- cbb cbc cbi cbo cbr cbt ccb ccc cci cco ccr cct ci- cib cic cii cio cir cit co- cob coc coi coo cor cot crb crc cri cro crr crt ctb ctc cti cto ctr ctt ibb ibc ibi ibo ibr ibt icb icc ici ico icr ict iib iic iii iio iir iit io- iob ioc ioi ioo ior iot ir- irb irc iri iro irr irt itb itc iti ito itt o-i ob- obb obc obi obo obr obt oc- ocb occ oci oco ocr oct oib oic oii oio oir oit oo- oob ooc ooi ooo oor oot or- orb orc ori oro orr ort ot- otb otc oti oto otr ott rbb rbc rbi rbo rbr rbt rcb rcc rci rco rcr rct rib ric rii rio rir rit rob roc roi roo ror rot rrb rrc rri rrr rrt rtb rtc rti rto rtr rtt tbb tbc tbi tbo tbr tbt tcb tcc tci tco tcr tct tib tic tii tio tir tit to- tob toc toi too tor tot trb trc tri tro trr trt ttb ttc tti tto ttr ttt