1259 : Fibbonacci Number

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. 

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

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

3
4
5
-1

2
3
5