Joan spent almost all of her holiday sunbathing on the roof of her hotel. 

She wore a bathing suit the first day, but on the second, she decided that no one could see her way up there, and she slipped out of it for an overall tan. 

She'd hardly begun when she heard someone running up the stairs. She was lying on her stomach, so she just pulled a towel over her rear. 

"Excuse me, miss," said the flustered assistant manager of the hotel, out of breath from running up the stairs. "The hotel doesn't mind you sunbathing on the roof, but we would very much appreciate your wearing a bathing suit as you did yesterday." 

"What difference does it make?" Joan asked rather calmly. "No one can see me up here, and besides, I'm covered with a towel." 

"Not exactly," said the embarrassed man. "You're lying on the dining room skylight."