LeetCode 1140 Stone Game II - Problem Statement

Piles of stones in a row. Players alternate taking $X$ piles from the front, where $1 \leq X \leq 2M$. After taking, $M$ becomes $\max(M, X)$. Initially $M = 1$. Both play optimally.

What's the max stones Player 1 can get? Example: piles $= [2, 7, 9, 4, 4]$, $M = 1$. Player 1 can take $1$ or $2$ piles. Taking $2$ gives $2 + 7 = 9$ stones and sets $M = 2$. Now Player 2 can take $1$ to $4$ piles... The variable $M$ adds a new dimension to the state. This problem combines interval-style thinking with an extra parameter.