20. In North Ridge, all the streets run east-west or north-south from one edge of town to the opposite edge of town. North Ridge is mapped onto a standard (x, y) coordinate plane where each coordinate unit represents 1 block. Charles lives at the corner (5, 6). Hortensia lives at the corner (1, 3). What is the minimum number of blocks Hortensia can walk to reach Charles's home, walking only along the streets of North Ridge?