KöMaL 2024 B5376

Let us divide positive integer $n$ with all the positive integers smaller than $n$, and let $f(n)$ denote the sum of the remainders we've obtained. (For example, when we divide $n=5$ by $1$, $2$, $3$ and $4$, we get remainders $0$, $1$, $2$ and $1$, respectively, therefore $f(5)=4$.) Solve equation $f(n)=n$.