func findLUSlength(a string, b string) (cnt int) {
	m, n := len(a), len(b)
	if m != n {
		if m < n {
			return n
		}
		return m
	} else {
		for i := range a {
			if a[i] != b[i] {
				return m
			}
		}
		return -1
	}
}