Question 1
a. Can you arrange the numbers $0, 1, \ldots, 9$ on the circumference of a circle, so that the difference between every pair of adjacent numbers is $3$, $4$ or $5$? For example, we can arrange the numbers $0, 1, \ldots, 6$ thus: $0, 3, 6, 2, 5, 1, 4$.
b. What about the numbers $0, 1, \ldots, 13$?
b. What about the numbers $0, 1, \ldots, 13$?