type pair struct {
	_1 int
	_2 int
}

func maxProduct(words []string) (product int) {
	n := len(words)
	if n <= 1 {
		return
	}
	pairs := make([]pair, n)
	for i := 0; i < n; i++ {
		mask, l := 0, len(words[i])
		for j := 0; j < l; j++ {
			mask |= 1 << uint(words[i][j]-'a')
		}
		pairs[i] = pair{mask, l}
	}
	for i := 0; i < n-1; i++ {
		for j := i + 1; j < n; j++ {
			if pairs[i]._1&pairs[j]._1 == 0 && product < pairs[i]._2*pairs[j]._2 {
				product = pairs[i]._2 * pairs[j]._2
			}
		}
	}
	return
}