b-p bbb bbp bbr bbs bbt bpb bpp bpr bps bpt brb brp brr brs brt bsb bsp bsr bss bst btb btp btr bts btt p-p pbb pbp pbr pbs pbt ppb ppp ppr pps ppt prb prp prr prs prt ps- psb psp psr pss pst pt- ptb ptp ptr pts ptt rbb rbp rbr rbs rbt rpb rpp rpr rps rpt rrb rrp rrr rrs rrt rsb rsp rsr rss rst rtb rtp rtr rts rtt sbb sbp sbr sbs sbt spb spp spr sps spt sr- srb srp srr srs srt ss- ssb ssp ssr sss sst stb stp str sts stt tbb tbp tbr tbs tbt tpb tpp tpr tps tpt trb trp trr trs trt tsb tsp tsr tss tst ttb ttp ttr tts ttt