You can
put this solution on YOUR website!On second thought:
If the natural number is a multiple of three, it can be written
as a sum of three numbers, each of which is one-third the original
number. If that sum is not used, one of the numbers in the sum
must be less than one-third the original number.
------------
If the natural number is not a multiple of three, at least one
of the numbers in the sum must be less than one-third the original
number.
------------
Stan H.
Cheers,