Given an integer n, return the nth ugly number. Ugly number is a positive number whose prime factors only include 2, 3, and/or 5. Example 1: Input: n = 10 Output: 12 Explanation: [1, 2, 3, 4, 5, 6, 8, 9, 10, 12] is the sequence of the first 10 ugly numbers. Example 2: Input: n = 1 Output: 1 Explanation: 1 is typically treated as an ugly number. Constraints: 1 <= n <= 1690