Digital Abacus

Whenever you draw a card, put a counter on
digital abacus. Whenever you discard a card,
remove a counter from digital abacus.
{t} Look at the top x cards of your library,
where x is the number of counters on digital
abacus. Without changing their order, put one
of those cards into your hand, and replace it
with digital abacus.
If X is 0, exile digital abacus.