A person is wandering in woods and records his movements as a sequence of displacements: d1 is 351 m, 35.0° north of east; d2 is 252m, 55.0° west of north; d3 is 178 m, 35.0° south of west; and d4 is 253 m, 15.0° north of west. Find his displacement going back to his starting point straight.