c-- ccc ccd ccr ccs cct cdc cdd cdr cds cdt crc crd crr crs crt csc csd csr css cst ctc ctd ctr cts ctt dcc dcd dcr dcs dct ddc ddd ddr dds ddt drc drd drr drs drt dsc dsd dsr dss dst dtc dtd dtr dts dtt rcc rcd rcr rcs rct rdc rdd rdr rds rdt rrc rrd rrr rrs rrt rsc rsd rsr rss rst rtc rtd rtr rts rtt scc scd scr scs sct sdc sdd sdr sds sdt sr- src srd srr srs srt ss- ssc ssd ssr sss sst stc std str sts stt tcc tcd tcr tcs tct tdc tdd tdr tds tdt trc trd trr trs trt tsc tsd tsr tss tst ttc ttd ttr tts ttt