leetcode1003

class Solution:
    def isValid(self, S: str) -> bool:
        n = len(S)
        if n % 3 != 0:
            return False
        while n!=0:
            i = S.find('abc')
            if i == -1:
                return False
            else:
                S = S[0:i] + S[i+3:]
                n = len(S)
        return True