Fredric Brown, a prolific and acclaimed writer of mystery and science fiction stories and novels, was an extraordinary master of the short-short. "Naturally" is a one-pager about Henry Blodgett, who knows he will fail his forthcoming geometry exam, flunk out of college, and ruin his career prospects. But Henry has studied black magic, and he's now desperate enough to risk summoning up a demon. It works! Henry starts to explain things, but gets interrupted:

"I've always been poor at geometry," he began... "You're telling me," said the demon gleefully.

Naturally the demon is gleeful, considering the geometric ineptitude of the pentagram that was meant to constrain him.