Josh, Sentient Elemental

{1}{g/u}{g/w}, Remove a +1/+1 counter from a
creature you control: Put a +1/+1 counter on
up to two target creatures.
When Josh, Sentient Elemental leaves the
battlefield double the number of +1/+1 counters
on any number of target creatures.
Whenever you put a +1/+1 counter on a target
creature, put another +1/+1 counter on
that creature.