-er a-a a-c a-t aaa aac aae aap aar aat aax ac- aca acc ace acp acr act acx aea aec aee aep aer aet aex ap- apa apc ape app apr apt apx ar- ara arc are arp arr art arx at- ata atc ate atp atr att atx ax- axa axe axp axr axt axx c-- caa cac cae cap car cat cax cca ccc cce ccp ccr cct ccx ce- cea cec cee cep cer cet cex cpa cpc cpe cpp cpr cpt cpx cra crc cre crp crr crt crx cta ctc cte ctp ctr ctt ctx cxc cxp cxr cxt cxx eaa eac eae eap ear eat eax ec- eca ecc ece ecr ect ecx eea eec eee eep eer eet eex ep- epa epc epe epp epr ept epx era erc ere erp err ert eta etc ete etp etr ett etx ex- exa exc exe exp exr ext exx p-p paa pac pae pap par pat pax pca pcc pce pcp pcr pct pcx pea pec pee pep per pet pex ppa ppc ppe ppp ppr ppt ppx pra prc pre prp prr prt prx pt- pta ptc pte ptp ptr ptt ptx pxc pxe pxr pxt ra- raa rac rae rap rar rat rax rca rcc rce rcp rcr rct rcx re- rea rec ree rep rer ret rex rpa rpc rpe rpp rpr rpt rpx rra rrc rrp rrr rrt rta rtc rte rtp rtr rtt rtx rxp rxr t-x taa tac tae tap tar tat tax tca tcc tce tcp tcr tct tcx te- tea tec tee tep ter tet tex tpa tpc tpe tpp tpr tpt tpx tra trc tre trp trr trt trx tta ttc tte ttp ttr ttt ttx txe txt xaa xac xap xar xat xcp xcr xcx xee xep xer xet xex xpa xpc xpe xpp xpt xrc xrt xrx xtc xtp xtr xtx xxp xxx