class Solution:
    def countBinarySubstrings(self, s: str) -> int:
      cnts = []
      i = 0
      j = 1
      while i < len(s) and j < len(s):
        if s[j] != s[i]:
          cnts.append(j-i)
          i = j
          j = i + 1 
        else:
          j += 1
      cnts.append(j-i)
      res = 0
      for k in range(1,len(cnts)):
        res += min(cnts[k], cnts[k-1])
      return res