It is not clear at least 2 points:

1) "The output should contain the maximal total rating of the guests."
President is the host, not a guest, so his rating is excluded. (?)

2) As the party is the president's anniversary he cannot absent. (?)

Am i right? If not, correct the condition please.

Answers to questions
1) President's rating should be included if he goes
2) President may not be at a party
3) Noone may go to the party

P.S. I'm not an admin :)