bzoj#P1522. [POI2006]Kry
[POI2006]Kry
题目描述
给定 个数 ,求一个序列 满足:
1.任意 2. 3.
求这样序列的个数。
输入格式
The first line of the standard input contains the number of elements , .
The second, last line of the standard input contains positive integers , separated by single spaces,.
输出格式
Your programme should write one integer to the standard output - total number of different crystals that can be created. You can assume that this number is less than .
3
2 1 3
5