(Sometimes a second part is needed for clarification. )
The following morning, the student took his accustomed seat a few paces from the wall facing the rising sun. The master paced a circuit that kept him always equidistant from the student and the wall.
Before the sun stood overhead, the student finally achieved something akin to enlightenment. “Aha! ” he said. “Teacher I see now that you are diabolical. ”
Swiftly, the master administered a boot to the head, leaving the student a crumpled mess.
“You were almost right there. But math is still hard, though not quite as hard as my boot.”