Get Special String

Developers at Amazon are working on a text generation utility for one of their new products.

Currently, the utility generates only special strings. A string is special if there are no matching adjacent characters. Given a string s of length n, generate a special string of length n that is lexicographically greater than s. If multiple such special strings are possible, then return the lexicographically smallest string among them.

Notes:

• Special String: A string is special if there are no two adjacent characters that are the same.
• Lexicographical Order: This is a generalization of the way words are alphabetically ordered in dictionaries. For example, "abc" is lexicographically smaller than "abd" because 'c' comes before 'd' in the alphabet.

A string a is lexicographically smaller than a string b if and only if one of the following conditions holds:

• a is a prefix of b, but is not equal to b.
• In the first position where a and b differ, the character in a comes before the character in b in the alphabet. For example, "abc" is smaller than "abd" because 'c' comes before 'd'.

Important Considerations:

• If the character is 'z', it is the last character in the alphabet and cannot be increased further. The string should not wrap around to 'a after 'z'
• The output string must not have any adjacent characters that are the same.