Replace the question mark with a number

The firemen finally get a huge fire under control, and Chief Brown has all of his men accounted for except Olson and Rosolino. After a few minutes' search, the chief looks down an alley, and there's Rosolino, leaning over a trash can. His pants are down to his ankles, and Olson is banging away from behind.
Chief Brown says, "What the hell is going on?"
Olson says, "Rosolino passed out from smoke inhalation."
The chief says, "Smoke inhalation? You're supposed to give him mouth-to-mouth resuscitation!"
Olson says, "I did, Chief, but then one thing led to another..."