CMO 2021 Problem 6

Find $f: \mathbb{Z}_+ \rightarrow \mathbb{Z}_+$ , such that for any $x,y \in \mathbb{Z}_+$ , $f(f(x)+y)\mid x+f(y).$

Dataset text AI-MO AoPS. Quoted with source.

Solutions

No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.