MATH PUZZLE: Can you replace...

A beautiful young girl is about to undergo a minor operation. She's laid on a hospital trolley bed with nothing on, except a sheet over her. The nurse pushes the trolley down the corridor towards the operating theatre, where she leaves the girl on the trolley outside, while she goes in to check whether everything is ready. A young man wearing a white coat approaches, lifts the sheet up and starts examining her naked body. He puts the sheet back and then walks away and talks to another man in a white coat. The second man comes over, lifts the sheet and does the same examinations. When a third man does the same thing, but more closely, she grows impatient and says: "All these examinations are fine and appreciated, but when are you going to start the operation?"
The man in the white coat shrugged his shoulders: "I have no idea. We're just painting the corridor."