Square Bob lives in a square town which is divided into a grid of 11 streets running north-south and 11 streets running east-west.  Bob lives in the soutwest corner of the town and every day runs to the northeast corner of town to play basketball.  One day, Bob decides to take a different route from home to the basketball court. The next day Bob takes a different route again.  If Bob only moves north or east at every street intersection, how many days will it take Bob to exhaust the different routes from home to the basketball court?