Your great aunt just took you for lunch at Josephine's and you are going to walk to the post office in downtown Flagstaff to mail a letter. Josephines is at the corner of Elm and Humphreys. The Post Office is 4 blocks south and 4 blocks east at the corner of Aspen and WC RIles.
How many different routes are there if you only allow yourself to walk south or east along any block? (Avoiding alleys and shortcuts.)