深搜回溯-素数环-1459-jobdu

题目1459：Prime ring problem
时间限制：2 秒内存限制：128 兆特殊判题：否提交：747解决：306
题目描述：
A ring is compose of n 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.

输入：
n (1 < n < 17).
输出：
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. Print solutions in lexicographical order.
You are to write a program that completes above process.
Print a blank line after each case.
样例输入：
6
8
样例输出：
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
提示：
用printf打印输出。