Rescue Son

Amit and his son are staying in a hotel which has M floors and N rooms on each floor. From each room, he can go in two other rooms, the room which is just below that room and the room which is just right to that room. Amit’s son has been kidnapped and kept in a room of that hotel. Amit is present in the leftmost room on the topmost floor of that hotel. But the room is locked and to open this room