Find K s.t. $\int_{\Omega}|K-f(x)|(K-f(x))=0$

Question

I'm trying to solve the following problem:

Let $\Omega$ a bounded set of $\mathbb{R}$, $f\in L^3(\Omega)$. Find $K\in\mathbb{R}$ such that

$\int_{\Omega}|K-f(x)|(K-f(x))=0.$

I'dont know how to begin. My first idea was to split the integral where $K-f(x)$ is lower or greater then 0 but in this way I couldn't conclude anything. Any help?