What is the relationship between Baidu and Beijing 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.

The tax-hailing app's Chinese unit currently operates in almost 20 cities, Mr Kalanick said at an event in Beijing held by Uber investor Baidu (Xetra: A0F5DE - news ) .

Answer: headquarters_location