## Fibonacci Sequence

The Fibonacci Sequence is computed as `f(n) = f(n-1) + f(n-2)`

. We must define two **base case** values: `f(0) = 0`

and `f(1) = 1`

.

Thus, the first values of this sequence are: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, etc.

Your task is to write a function `fib`

which takes a single number `n`

and returns `f(n)`

as defined above by the Fibonacci Sequence.