青蛙跳台阶问题（斐波那契数列） python

一只青蛙一次可以跳上1级台阶，也可以跳上2级。求该青蛙跳上一个n级的台阶总共有多少种跳法

class Solution:
    def jump(self,n):
        if n ==0:
            return 0
        elif n==1:
            return 1
        elif n ==1:
            return 2
        numN = 0
        first = 1
        second = 2
        for i in range(3,n+1):
            numN = first+second
            first = second
            second = numN
        return numN

if __name__ =='__main__':
    solution = Solution()
    time = solution.jump(5)
    print(time)