The Fibonacci series: 0, 1, 1, 2, 3, 5, 8, 13, 21, has as its first 2 values, 0 and 1; each successive value if then calculated as the sum of the previous two values. The first element in the series is the 0'th element, thus the value 8 is element 6 of the series. The n'th element of the series, written as fib(n), is thus defined as:
n if n = 0 or n = 1
fib(n-1) + fib(n-2)

Write the int -valued function fib, that takes a single int parameter (say n), and recursively calculates and then returns the n'th element of the Fibonacci series.