Question 6.6 from the course text.
0 | 2-1-3-5-4-9-12-6-8-10-15-13 | | | 11 14 7
/ 0 0 0 0 0 0 6 0 0 0 9 0 0 12 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15