The Fibonacci sequence is the series of integers

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89

See the pattern? Each element in the series is the sum of the preceding two items.

There is a recursive formula for calculating the nth number of the sequence (the oth

number if Fib(0)=0):

Fib(N) = / N, if N=0 or 1

\ Fib(N-2) + Fib(N-1), if N > 1

Write a nonrecursive version of the function Fibonacci