Script

When Script enters the battlefield, put a 1/1 Artifact Construct Creature token into the battlefield.
If you have one creature, put a 1/1 Counter on that creature.
If you have 2 creatures, put a 2/2 Counter on one of those creatures.
If you have 3 creatures, put a 3/3 Counter on one of those creatures.
If you have 4 creatures, put a 4/4 Counter on one of those creatures.