bbb bbi bbr bbs bbt bi- bib bii bir bis bit brb bri brr brs brt bsb bsi bsr bss bst btb bti btr bts btt ibb ibi ibr ibs ibt iib iii iir iis iit ir- irb iri irr irs irt is- isb isi isr iss ist itb iti its itt rbb rbi rbr rbs rbt rib rii rir ris rit rrb rri rrr rrs rrt rsb rsi rsr rss rst rtb rti rtr rts rtt sbb sbi sbr sbs sbt sib sii sir sis sit sr- srb sri srr srs srt ss- ssb ssi ssr sss sst stb sti str sts stt tbb tbi tbr tbs tbt tib tii tir tis tit trb tri trr trs trt tsb tsi tsr tss tst ttb tti ttr tts ttt