Largest Lexicographical Substring

Given two strings A and B , your task is to output the largest lexicographically ordered substring of string B that makes string B a superstring of string A . If no such substring exists, output -1 .

A superstring is a string that contains all the characters present in another string, irrespective of their order.

Example 1 :

Input:
A = "abc", B = "abcab"
Output:
"cab"
Explanation:
String B is a superstring of string A because it contains all the
characters of A in various sequences. Among these sequences, ("cab", "abc", "bca")
meet the conditions, and the largest lexicographically ordered substring among them is "cab".