P________O________S________T
pOsT
P___O______S_________T
P.......O.......S.......T
"P"...."O"...."S"...."T"
P & O & S & T
<P>O<S>T<
p + O = S - t = post
psot
{P} [O] {S} [T]
postpotspsotpstoptsoptos