You’re given an N * N array, and asked to fill it with consecutive
integers, starting with 1 in the center cell, then moving down one
to put a 2, then left to put a 3, up to put 4 and then 5, then right
for 6 and 7, and so on until you’ve filled the array.

# 7x7:
# .  .  .  .  .  .  .
# .  .  .  .  .  .  .
# .  .  5  6  7  .  .
# .  .  4  1  8  .  .
# .  .  3  2  9  .  .
# .  .  . <- 10  .  .
# .  .  .  .  .  .  49