# Day 4 of July LeetCode Challenge

Write a program to find the `n`

-th ugly number.

Ugly numbers are** positive numbers** whose prime factors only include `2, 3, 5`

.

**Example:**

**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.

**Note:**

`1`

is typically treated as an ugly number.`n`

**does not exceed 1690**.