Reiner Braun, Titanshifter

Reiner Braun, Titanshifter enters the
battlefield with two +1/+1 counters on it.
When Reiner Braun, Titanshifter attacks,
put a +1/+1 counter on it.
At the beginning of your end step if Reiner
Braun, Titanshifter has four or more +1/+1
counters, transform it.