Analyze the relationship between 'Syriza' and 'ATHENS' within the context of the input sentence.
Options: creator, employer, headquarters location, parent organization

ATHENS (Reuters) - Rebels angered by Greece's international bailout walked out of the leftist Syriza party on Friday, formalising a widely-expected split after leader Alexis Tsipras resigned as prime minister to pave the way for early elections.
headquarters location