A neutron walks into a bar and asks the bartender for a bottle of Heineken. He asks, "How much will it cost?"
The bartender says, "For you, no charge."
Then the neutron's friend, the proton, walks up to the bar and asks for a shot of whiskey, a shot of vodka, and a shot of rum. The bartender asks, "Are you sure?"
The proton says, "Yes, I'm positive."