Akka Prime

Bob is a very lazy boy. He always sleeps in Maths class. One day his teacher catches him sleeping and tells him that she would mark him absent for the whole semester. While she pretends to be strict, she is actually very kind-hearted. So she wants to give Bob a chance to prove himself. She gives him a problem. If Bob can answer it correctly, she will forgive him. Can you help Bob find the answer t