The k-th Lexicographical String of All Happy Strings of Length n

A "happy string" consists of characters 'a', 'b', 'c' where no two adjacent characters are the same. Given n and k, return the k-th lexicographical happy string of length n.

Examples
Input: [1,3]
Output: "c"
Hints

The k-th Lexicographical String of All Happy Strings of Length n

A "happy string" consists of characters 'a', 'b', 'c' where no two adjacent characters are the same. Given n and k, return the k-th lexicographical happy string of length n.