Davenport constant formula for intervals containing zero

Let $m$ and $M$ be positive integers, and let $\mathsf{D}(\llbracket -m,M \rrbracket)$ denote the maximal length of a minimal zero-sum sequence with terms in $\llbracket -m,M \rrbracket$. Define

$$\chi(\llbracket -m,M \rrbracket)=\sup_{x,y\in\llbracket -m,M \rrbracket\text{ with }xy<0}\frac{|x|+|y|}{\gcd(x,y)}.$$

Davenport constant conjecture for intervals.

$$\mathsf{D}(\llbracket -m,M \rrbracket)=\chi(\llbracket -m,M \rrbracket).$$

This conjecture gives a general formula for the Davenport constant of an interval of integers containing zero. The source paper states that it proves this conjecture, so the claim is solved.