I SAT ON A ROCK!!!!1111

I SAT ON A ROCK!!!!1111 enters the battlefield with X rock counters on it.
Whenever a player sits down, remove a rock counter from I SAT ON A ROCK!!!!1111 and put a +1/+1 counter on it.
I SAT ON A ROCK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!111111111111111111111111111111111111111111111111111111111111111