Foreststomper Hydra

Foreststomper Hydra enters the battlefield with X +1/+1 counters on it.
Whenever Foreststomper Hydra is dealt damage, put double that many +1/+1 counters on it in the next end step.
As long as Foreststomper Hydra has five or more +1/+1 counters on it, it has trample.