type strslice []string

func (ss strslice) Len() int           { return len(ss) }
func (ss strslice) Less(i, j int) bool { return len(ss[j]) < len(ss[i]) }
func (ss strslice) Swap(i, j int)      { ss[i], ss[j] = ss[j], ss[i] }

func findLUSlength(strs []string) int {
	sort.Sort(strslice(strs))
	m := make(map[string]int)
	for i := range strs {
		m[strs[i]]++
	}
	for i := range strs {
		if val, _ := m[strs[i]]; val == 1 {
			j := 0
			for ; j < i && !isSubstr(strs[j], strs[i]); j++ {
			}
			if j == i {
				return len(strs[i])
			}
		}
	}
	return -1
}

func isSubstr(s, t string) bool {
	i, j, m, n := 0, 0, len(s), len(t)
	s1, s2 := []rune(s), []rune(t)
	for ; i < m && j < n; j++ {
		for ; i < m && s1[i] != s2[j]; i++ {
		}
		i++
	}
	return i <= m && j == n
}