text: class Solution:
      def minRemoveToMakeValid(self, s: str) -> str:
          if not s :
              return ""
          s = list(s)
          st = []
          
          for i,n in enumerate(s):
              if n == "(":
                  st.append(i)
              elif n == ")" :
                  if st :
                      st.pop()
                  else :
                      s[i] = ""
              
          while st:
              s[st.pop()] = ""
          return "".join(s)
          
                  
              
          
  