题解 | #斐波那契数列#

# -*- coding:utf-8 -*-
class Solution:
    def Fibonacci(self, n):
        f1,f2,sum = 1,1,0
        if n==0:
            return 0
        if n <= 2:
            return f1
        for i in range(n-2):
            sum = f1 + f2
            f1 = f2
            f2 = sum
        return sum
        # write code here
num = int(input())
s = Solution()
print(s.Fibonacci(num))