Computer Transformation

描述
A sequence consisting of one digit, the number 1 is initially written into a computer. At each successive time step, the computer simultaneously tranforms each digit 0 into the sequence 1 0 and each digit 1 into the sequence 0 1. So, after the first time step, the sequence 0 1 is obtained; after the second, the sequence 1 0 0 1, after the third, the sequence 0 1 1 0 1 0 0 1 and so on.

How many pairs of consequitive zeroes will appear in the sequence after n steps?
输入
Every input line contains one natural number n (0 < n ≤1000).
输出
For each input n print the number of consecutive zeroes pairs that will appear in the sequence after n steps.
样例
样例输入 #1
2
3
样例输出 #1
1
1
来源
Southeastern Europe 2005
HDOJ-1041
题目来源:HDOJ-1041
时间限制:1000 MS
内存限制:32768 KB
Java 类名:Main
64 位整数占位符:%I64d