What is the relationship between Lyft and San Francisco 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.

San Francisco startup Lyft Inc. and Chinese startup Didi Kuaidi Joint Co. said Wednesday they have formed an alliance to allow users of each app to hail rides from drivers of the other app while they are traveling to the other country.

Answer: headquarters_location