eee eel eem eet eex ele ell elm elt elx em- eme eml emm emt emx ete etl etm ett etx ex- exe exl ext exx lee lel lem let lex lle lll llm llt lme lml lmm lmt lte ltl ltm ltt ltx lxx mee mel mem met mex mle mll mlm mlt mlx mme mml mmm mmt mmx mte mtl mtm mtt mtx mxl t-x te- tee tel tem tet tex tle tll tlm tlt tlx tme tml tmm tmt tmx tte ttl ttm ttt ttx txe txl txt xee xel xem xet xex xlm xlt xml xmm xmt xmx xtm xtx xxl xxx