Problem Description

Your objective for this question is to develop a program which will generate a fibbonacci number. The fibbonacci function is defined as such:

$f(0) = 0$

$f(1) = 1$

$f(n) = f(n-1) + f(n-2)$

Your program should be able to handle values of $n$ in the range 0 to 50.

Input

Each test case consists of one integer $n$ in a single line where $0≤n≤50$. The input is terminated by -1.

Output

Print out the answer in a single line for each test case.

Samples

3
4
5
-1

2
3
5