Utilize the input text as a context reference, choose the right relationship between 'Syriza' and 'ATHENS' from the options.
Options: operator, stock exchange, headquarters location, owner of

ATHENS Aug 21 Greece's new Popular Unity party of far-left rebels from the leftist Syriza party will seek a mandate to form a government as the third-biggest group in parliament, a senior party lawmaker told Reuters on Friday.
headquarters location