Take me a while to think through the problem, even had the doubt whether it is a
easy problem at all. Then suddenly I realized when
a != b, the longer one can never be the subsequence of the short one. What a joke! Anyway, happy April Fools' day.
class Solution(object): def findLUSlength(self, a, b): """ :type a: str :type b: str :rtype: int """ return -1 if a == b else max(len(a), len(b))