oo- ooo oop oos oot oox op- opo opp ops opt opx os- oso osp oss ost osx ot- oto otp ots ott ox- oxo oxt oxx p-p poo pop pos pot pox ppo ppp pps ppt ppx ps- pso psp pss pst psx pt- pto ptp pts ptt ptx pxs pxt soo sop sos sot sox spo spp sps spt spx ss- sso ssp sss sst ssx sto stp sts stt stx sxs sxt t-x to- too top tos tot tox tpo tpp tps tpt tpx tso tsp tss tst tsx tto ttp tts ttt ttx txs txt xoo xop xos xot xox xpo xpp xps xpt xsp xss xst xtp xts xtx xxo xxp xxx