hink of that allows
reiteration requires that the grain size change -- but that is,
as you point out, not physically realistic, as grains do have
a minimum size. So formalization of the reiterative process 
with a single definition of "heap" is impossible (any attempt
results in an untrue statement), and formalization of the 
intuition must require that the resulting pile be different from 
the starting pile, regardless of whether at early iterations 
it might be possible to refer to the starting and result