# 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