# power series – Obtain the initial value of a sum with known formula and result?

I am currently studying programming and one of the problems that I wanted to obtain the initial value $$n$$ of the next sum I know the result $$m$$ (The problem is not exactly this, but I turned the problem into this):

$$sum_ {x = 0} ^ {n-1} (n-x) ^ {3} = m$$

I'm posting this here instead of a programming site because I don't want the answer in the code, but only the math behind it. I would do it myself, but I'm still in high school and I haven't seen anything like that before, so if someone could explain to me how I would do this, or maybe just tell me what to look for to learn how to do these things, it would be greatly appreciated.

Also, since I don't know exactly what branch of mathematics this is, I don't know what label to use, so if I was wrong, let me know.