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