What is the relationship between Highmark and Pittsburgh in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

On the commercial side, in Q2, we improve net coverage within two prominent regional commercial plans, Highmark Blue Cross Blue Shield and the University of Pittsburgh Medical Center or UPFC.

Answer: headquarters_location