bbb bbe bbo bbs bbt be- beb bee beo bes bet bob boe boo bos bot bsb bse bso bss bst btb bte bto bts btt ebb ebe ebo ebs ebt eeb eee eeo ees eet eo- eob eoe eoo eos eot es- esb ese eso ess est etb ete eto ets ett ob- obb obe obo obs obt oeb oee oeo oes oet oo- oob ooo oos oot os- osb ose oso oss ost ot- otb ote oto ots ott sbb sbe sbo sbs sbt se- seb see seo ses set sob soe soo sos sot ss- ssb sse sso sss sst stb ste sto sts stt tbb tbe tbo tbs tbt te- teb tee teo tes tet to- tob toe too tos tot tsb tse tso tss tst ttb tte tto tts ttt