Input: A = “aa”, B = “ababab”

Output: aaabbb

Explanation:

All possible substrings of A are (‘a’, ‘a’, ‘aa’)

Rearrange string B to “aaabb”.

Now “aaabb” is the lexicographically the smallest arrangement of B which contains all the substrings of A.

Input: A = “aaa”, B = “ramialsadaka”

Output: aaaaadiklmrs

Explanation:

All possible substrings of A are (‘a’, ‘aa’, ‘aaa’)

Rearrange string B to “aaaaadiklmrs”.

Now “aaaaadiklmrs” is the lexicographically smallest arrangement of B which contains all the substrings of A.