eee eeo eep eet eex eo- eoe eoo eop eot ep- epe epo epp ept epx ete eto etp ett etx ex- exe exo exp ext exx oee oeo oep oet oex oo- ooo oop oot oox op- ope opo opp opt opx ot- ote oto otp ott ox- oxo oxt oxx p-p pee peo pep pet pex poe poo pop pot pox ppe ppo ppp ppt ppx pt- pte pto ptp ptt ptx pxe pxt t-x te- tee teo tep tet tex to- toe too top tot tox tpe tpo tpp tpt tpx tte tto ttp ttt ttx txe txt xee xep xet xex xoo xop xot xox xpe xpo xpp xpt xtp xtx xxo xxp xxx