text: class Solution:
      def climbStairs(self, n: int) -> int:
          if n == 1:
              return 1
          elif n == 2:
              return 2
          else:
              a = 1
              b = 2
              while(n - 2 > 0):
                  b = a + b
                  a = b - a
                  n -= 1
                  
              return b;
          
          