# Out of the line!

Very easy

Execution time limit is 1 second

Runtime memory usage limit is 128 megabytes

$n$ soldiers stay in one line. In how many ways can we choose some of them (at least one) so that among them there will not be soldiers standing beside?

## Input

One number $n(1≤n≤90)$.

## Output

Print one number — the answer to the problem.

## Examples

Input #1

Answer #1

Input #2

Answer #2

Input #3

Answer #3

Submissions 4K

Acceptance rate 43%