bbb bbc bbn bbo bbr bbs bcb bcc bcn bco bcr bcs bnb bnc bnn bno bnr bns bob boc bon boo bor bos brb brn bro brr brs bsb bsc bsn bso bsr bss c-- cbb cbc cbn cbo cbr cbs ccb ccc ccn cco ccr ccs cn- cnb cnc cnn cno cnr cns co- cob coc con coo cor cos crb crc crn cro crr crs csb csc csn cso csr css nbb nbc nbn nbo nbr nbs ncb ncc ncn nco ncr ncs nnb nnc nnn nno nns no- nob noc non noo nor nos nrb nrc nrn nro nrr nrs nsb nsc nsn nso nsr nss ob- obb obc obn obo obr obs oc- ocb occ ocn oco ocr ocs on- onb onc onn ono onr ons oo- oob ooc oon ooo oor oos or- orb orc orn oro orr ors os- osb osc osn oso osr oss rbb rbc rbn rbo rbr rbs rcb rcc rcn rco rcr rcs rnb rnc rnn rno rnr rns rob roc ron roo ror ros rrb rrc rrn rrr rrs rsb rsc rsn rso rsr rss sbb sbc sbn sbo sbr sbs scb scc scn sco scr scs snb snc snn sno snr sns sob soc son soo sor sos sr- srb src srn sro srr srs ss- ssb ssc ssn sso ssr sss