text: class Solution:
      def lengthOfLongestSubstring(self, s):
          """
          :type s: str
          :rtype: int
          """
          if len(s) == 0:
              return 0
          m = 0
          idx = 0
          
          while idx < len(s)-m:
              substring = ''
              u = idx
              while u < len(s) and s[u] not in substring :
                  substring += s[u]
                  u += 1
              m = max(len(substring),m)
              
              idx += 1
              
          return m
  
  toto = Solution()
  print(toto.lengthOfLongestSubstring("pwwkew"))