MathNet 2015-part-07 — 185 problems (EN–VI) Question 116

Let $f: \mathbb{R}^{+} \rightarrow \mathbb{R}$ be a continuous function satisfying $f(x y)=f(x)+f(y)+1$ for all positive reals $x, y$. If $f(2)=0$, compute $f(2015)$.