36. (1)(4)(5).
36. Let the domain of the function $f(x)$ be R. If there exists a constant $m>0$ such that $|f(x)| \leqslant m|x|$ holds for all real numbers $x$, then $f(x)$ is called an $F$ function. Given the following functions:
(1) $f(x)=0$; (2) $f(x)=x^{2}$; (3) $f(x)=\sqrt{2}(\sin x + \cos x)$; (4) $f(x)=\frac{x}{x^{2}+x+1}$; (5) $f(x)$ is an odd function defined on R, and satisfies for all real numbers $x_{1}, x_{2}$, $\mid f\left(x_{1}\right) - f\left(x_{2}\right)| \leqslant 2| x_{1} - x_{2}!$. Among these, the functions that are $F$ functions are $\qquad$