Confronting a Circle

Monk "A" asked monk "B" for an answer to the famous Koan of Chinese zen master Majo. ( That is to ask a student, after drawing a circle on the ground before him, "You'll be struck hard 30 times, if you go into this circle or not." ) Thereupon, monk "B" erased the circle with his feet. Monk "A" said, "You are mistaken. How could you have kept your life under the strikes of Majo, then."

What would you do ?