Leetcode: Climbing Stairs @Python

class Solution:
    # @param n, an integer
    # @return an integer
    def climbStairs(self, n):
        if n<2:
            return 1
        step1=1
        step2=1
        for i in range(2,n+1):
            temp1=step1+step2
            step2=step1
            step1=temp1
        return step1