## fib is to calculate the nth fibonacci number
## fibonacci numbers are characterized by the fact that
## every number after the first two is the sum of the two 
## preceding ones
## fibonacci numbers: 1, 1, 2, 3, 5, 8, 13 
## fib(0) == 1
## fib(1) == 1
## fib(2) == 2
## fib(3) == 3
## ..
def fib(n):
	if n == 1 or n == 0:
		return 1
	else:
		#add one line of codes here
		