A ring is compose of n (even number) circles as shown in
diagram. Put natural number 1, 2, ..., n into each circle
separately, and the sum of numbers in two adjacent circles should
be a prime.
Note: the number of first circle should always be 1.

n (0<n=<20)
The output format is shown as sample below. Each row represents a series of circle numbers in the ring beginning from 1 clockwisely and anticlockwisely. The order of numbers must satisfy the above requirements.
You are to write a program that completes above process.
6 8
Case 1: 1 4 3 2 5 6 1 6 5 2 3 4 Case 2: 1 2 3 8 5 6 7 4 1 2 5 8 3 4 7 6 1 4 7 6 5 8 3 2 1 6 7 4 3 8 5 2