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 an integer that is the result of multiplying a whole integer by itself. For example, $1$, $4$, $9$, and $16$ are perfect squares, but $3$, $5$, and $11$ are not.

Constraints:

• $1 \leq$ n $\leq 10^3$

One of the first solutions that comes to mind is to keep subtracting perfect squares (like $9$, ...