Is it possible to simulate a floor() function with elementary arithmetic?

Let
$$f_1(x)=x+c_1$$
$$f_2(x)=x\cdot c_2$$
where $c_1,c_2$ are some constants, and $f_1$ represents addition and subtraction, and $f_2$ represents multiplication and division. Functions $f_1$ and $f_2$ have inverse function, but $\lfloor{x}\rfloor$ does not have an inverse function. So, if we assume it is possible to find $\lfloor{x}\rfloor$ from $x$ using $f_1$ and $f_2$, then it is possible to find $x$ from $\lfloor{x}\rfloor$. Contradiction.