I always suggest calling the cops. That's their job. They don't mind it, and it gets the message across. If you try to confront them yourself, you may think you're being nice and giving them a chance to correct the problem without the police; but most of the time people in those situations are anything but reasonable. If it's a fight, they're stressed. If it's a party, they got the numbers on you, and you're the "loser" who can't handle a little party.

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I'm like one of those idiot savants...well, except for the savant part.