Given an integer `n`, return the least number of perfect square numbers that sum to `n`.

A perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, `1`, `4`, `9`, and `16` are perfect squares while `3` and `11` are not.

Example 1:

    Input: n = 12
    Output: 3
    Explanation: 12 = 4 + 4 + 4.

Example 2:

    Input: n = 13
    Output: 2
    Explanation: 13 = 4 + 9.

Constraints:

- `1 <= n <= 104`