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.
you can use 64bit integer: __int64