Find the K-th Character in String Game I

Alice and Bob are playing a game. Initially, Alice has a text word = "a" .

You receive a positive integer k .

Now Bob will ask Alice to perform the following operation forever:

• Generate a new text by changing each character in word to its next character in the English alphabet, and append it to the original word .

For example, performing the operation on "c" generates "cd" and performing the operation on "zb" generates "zbac" .

Produce the value of the k^th character in word , after enough operations have been done for word to have at least k characters.