Stalking Wurm

When Stalking Wurm enters the battlefield,
choose a basic land type.
Whenever a land of the chosen type enter the battlefield put a +1/+1 counter on Stalking
Wurm then if the land was non basic, put
X +1/+1 counters on Stalking Wurm ,
where X is the number of counters on
Stalking Wurm.