旗帜问题的排布

 

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Time Limit: 1000MS Memory limit: 65536K

题目描述

On the Day of the Flag of Russia a shop-owner decided to decorate the show-window of his shop with textile stripes of white, blue and red colors. He wants to satisfy the following conditions:

1.   Stripes of the same color cannot be placed next to each other.

2.   A blue stripe must always be placed between a white and a red or between a red and a white one.

Determine the number of the ways to fulfill his wish.

Example. For N = 3 result is following:

输入

N, the number of the stripes, 1 ≤ N ≤ 45.

输出

M, the number of the ways to decorate the shop-window.

示例输入

3

示例输出

4
一开始做的时候，并没有考虑大数据，以促使才知道竟然溢出了，想到用long long int，但还是不行，最后没想到用double就搞定了。注意一下输出即可  printf("%.0lf", f[n]);