*Problem #26*

##
You are given three stacks of cards having *a* cards, *b* cards,
and *c* cards respectively. At each turn, you are allowed to remove
3 cards from one of the stacks, but you must add 1 card to each
of the other stacks. For example, using ordered triples to denote the number
of cards in each stack, a possible sequence of moves is (3,1,4) to (0,2,5)
to (1,3,2) to (2,0,3) to (3,1,0) to (0,2,1) at which point the process
terminates. Give a (relatively) simple rule for determining, given
*a, b,* and *c*, what the final outcome will be.