Question: United States Forces – Iraq (USF-I) was an American military sub-unified command, part of U.S. Central Command, General Lloyd Austin served as Commanding General, he was the which number commander of United States Central Command (CENTCOM)? 
Sentence (from "Lloyd Austin"): Prior to his assignment in CENTCOM, Austin served as the 33rd Vice Chief of Staff of the United States Army from January 31, 2012, to March 8, 2013.
Relevant evidence: No