Let be the set of real numbers. Determine all functions such that, for any real numbers and ,
Let $\mathbb{R}$ be the set of real numbers. Determine all functions $f: \mathbb{R} \rightarrow \mathbb{R}$ such that, for any real numbers $x$ and $y$, \[ f(f(x)f(y)) + f(x+y) = f(xy). \]
Školjka 
be the set of real numbers. Determine all functions 
such that, for any real numbers 
and 
, 