Hard
An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5. Given an integer n, return the n-th ugly number. (The sequence 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, ... begins with 1.)
Input: n = 10 Output: 12
Input: n = 1 Output: 1