text: class Solution:
      def climbStairs(self, n: int) -> int:
          prev, cur = 1, 1
          if n < 2:
              return 1
          for i in range(2, n + 1):
              prev, cur = cur, prev + cur
          return cur
  
  
  if __name__ == '__main__':
      n = 3
      print(Solution().climbStairs(n))
  