Reorder the following words by special rules: White, Orange, Blue, Green, Yellow, Purple, Pink, and Black. Each rule specifies one word must be beside another one. After all rules are satisfied, arrange the words by alphabet order.

Sample Input: input.txt

3
Black is beside Pink
Yellow is beside Pink
Orange is beside White

Sample Output: output.txt

Black Pink Yellow Blue Green Orange White Purple

USACO编程竞赛概要：铜级题#3

给下面的单词按照特殊规则排序：White, Orange, Blue, Green, Yellow, Purple, Pink, Black。每一个规则要求一个单词和另外一个单词在一起。满足所有要求后，再按照字母顺序给其他单词排序。

输入样例：input.txt

3
Black is beside Pink
Yellow is beside Pink
Orange is beside White

输出样例：output.txt

Black Pink Yellow Blue Green Orange White Purple

Python Solution: