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at a white house gathering of aids activists and lawmakers from around the world , the president said hir plan could prevent 7 million new hiv infections -- and treat at least 2 million people over the next decade .
 ( meet: gathering,  white house: place, activists: entity, lawmakers: entity, president: entity) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: declare bankruptcy, transfer ownership, transfer money, marry, transport, die, phone write, arrest jail, convict, sentence, sue, end organization, start organization, end position, start position, meet, elect, attack, injure, born, fine, release parole, charge indict, extradite, trial hearing, demonstrate, divorce, nominate, appeal, pardon, execute, acquit, merge organization, Arguments type: beneficiary, prosecutor, plaintiff, seller, victim, buyer, agent, destination, artifact, organization, recipient, person, place, origin, target, giver, adjudicator, attacker, vehicle, defendant, entity, instrument. 
Text: {0} 
Answer:
 ( meet: gathering,  white house: place, activists: entity, lawmakers: entity, president: entity) 