A knight jumps around an infinite chessboard. The chessboard is an unexplored territory. In the spirit of explorers, whoever stands on a square for the first time claims the ownership of this square. The knight initially owns the square he stands, and jumps $N$ times before he gets bored.
Recall that a knight can jump in 8 directions. Each direction consists of two squares forward and then one squaure sidways.
After $N$ jumps, how many squares can possibly be claimed as territory of the knight? As $N$ can be really large, this becomes a nightmare to the knight who is not very good at math. Can you help to answer this question?