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