880. Decoded String at Index

You are given an encoded string s. To decode the string to a tape, the encoded string is read one character at a time and the following steps are taken: - If the character read is a letter, that letter is written onto the tape. - If the character read is a digit d, the entire current tape is repeatedly written d - 1 more times in total. Given an integer k, return the kth letter (1-indexed) in t