A scuba diver makes a slow descent into the depths of the ocean. His vertical position with respect to a boat on the surface changes several times. He makes the first stop, d1 from the boat but has a problem with equalizing the pressure so he ascends d2 and then continues descending for another d3 to the second stop. From there, he ascends d4 and then descends for d5, ascends again for d6 and descends again for d7, where he makes a stop waiting for his buddy. Assume the positive direction is up to the surface express his net vertical displacements (in m) in terms of the unit vector. What is his distance to the boat (in m)?