시간 제한메모리 제한제출정답맞힌 사람정답 비율
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## 문제

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?

## 입력

Every input line contains one natural number n (0 < n ≤ 1000).

## 출력

For each input n print the number of consequitive zeroes pairs that will appear in the sequence after n steps.

## 예제 입력 1

2
3


## 예제 출력 1

1
1