walking ballista enters the battlefield with x +1/+1 counters on it.
4: put a +1/+1 counter on walking ballista.
remove a +1/+1 counter from walking ballista: it deals 1 damage to any target.
4: put a +1/+1 counter on walking ballista.
remove a +1/+1 counter from walking ballista: it deals 1 damage to any target.
