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All leaked interview problems are collected from Internet.

Write a program to find the `n`

-th ugly number.

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

. For example, `1, 2, 3, 4, 5, 6, 8, 9, 10, 12`

is the sequence of the first `10`

ugly numbers.

Note that `1`

is typically treated as an ugly number, and *n* **does not exceed 1690**.

**Credits:**

Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

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