class Solution:
def climbStairs(self, n: int) -> int:
dp = [0] * (n + 1)
if n < 3:
return max(n, 1)
dp[0] = 1
dp[1] = 1
dp[2] = 2
for i in range(3, n + 1):
for j in range(1,3):
dp[i] += dp[i - j]
return dp[n]