An encoded string S is given. To find and write the decoded 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 (say d), the entire current tape is repeatedly written d-1 more times in total. Now for some encoded string S, and an index K, find and return the K-th letter (1 indexed) in the decoded string. Example 1: Input: S = "leet2code3", K = 10 Output: "o" Explanation: The decoded string is "leetleetcodeleetleetcodeleetleetcode". The 10th letter in the string is "o". Example 2: Input: S = "ha22", K = 5 Output: "h" Explanation: The decoded string is "hahahaha". The 5th letter is "h". Example 3: Input: S = "a2345678999999999999999", K = 1 Output: "a" Explanation: The decoded string is "a" repeated 8301530446056247680 times. The 1st letter is "a". Constraints: 2 <= S.length <= 100 S will only contain lowercase letters and digits 2 through 9. S starts with a letter. 1 <= K <= 10^9 It's guaranteed that K is less than or equal to the length of the decoded string. The decoded string is guaranteed to have less than 2^63 letters.