## 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.

## Sample Input:

3
4
5
-1

## Sample Output:

2
3
5
* *
you can use 64bit integer: __int64

## Note:

Note: