-er c-- ccc ccd cce ccf ccr ccs cdc cdd cde cdf cdr cds ce- cec ced cee cef cer ces cfc cfd cfe cff cfr cfs crc crd cre crf crr crs csc csd cse csf csr css dcc dcd dce dcf dcr dcs ddc ddd dde ddf ddr dds de- dec ded dee def der des dfc dfd dfe dff dfr dfs drc drd dre drr drs dsc dsd dse dsf dsr dss ec- ecc ecd ece ecf ecr ecs ed- edc edd ede edf edr eds eec eed eee eef eer ees ef- efc efd efe eff efr efs erc erd ere erf err ers es- esc esd ese esf esr ess fcc fcd fce fcf fcr fcs fdc fdd fde fdf fdr fds fec fed fee fef fer fes ffc ffd ffe fff ffr ffs frc frd fre frf frr frs fsc fsd fse fsf fsr fss rcc rcd rce rcf rcr rcs rdc rdd rde rdf rdr rds re- rec red ree ref rer res rfc rfd rfe rff rfr rfs rrc rrd rrf rrr rrs rsc rsd rse rsf rsr rss scc scd sce scf scr scs sdc sdd sde sdf sdr sds se- sec sed see sef ser ses sfc sfd sfe sff sfr sfs sr- src srd sre srf srr srs ss- ssc ssd sse ssf ssr sss