35. Count and Say

The count-and-say sequence is a sequence of digit strings defined by the recursive formula: - countAndSay(1) = "1" - countAndSay(n) is the run-length encoding of countAndSay(n - 1). Run-length encoding compresses a string by replacing each group of consecutive identical characters with the count followed by the character. Given a positive integer n, return the n-th element of the count-and-say sequence.