What is the relationship between chief and New York City 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.

HFF, Inc. ( HF ) announced that Mark Gibson , chief executive officer, will be participating in a panel discussion at the JMP Securities Financial Services & Real Estate Conference in New York City on Monday, September 21 st .

Answer: location_of_formation