Fibonacci Series

# Function for nth fibonacci
# number - Space Optimisation
# Taking 1st two fibonacci numbers as 0 and 1

def fibonacci(n):
	a = 0
	b = 1
	
	# Check is n is less
	# than 0
	if n < 0:
		print("Incorrect input")
		
	# Check is n is equal
	# to 0
	elif n == 0:
		return 0
	
	# Check if n is equal to 1
	elif n == 1:
		return b
	else:
		for i in range(1, n):
			c = a + b
			a = b
			b = c
		return b

# Driver Program
print(fibonacci(9))

# This code is contributed by Saket Modi
# Then corrected and improved by Himanshu Kanojiya