class Solution:
    def Fibonacci(self, n):
        # write code here
        if n == 0:
            return 0
        if n == 1:
            return 1
        fOne = 1
        fZero = 0
        for i in range(2,n+1):
            fN = fOne + fZero
            fZero = fOne
            fOne = fN
        return fN