We assume that for all $d \geqslant 0$, $\mathbb{P}(X \in d\mathbb{Z}) < 1$, and that $g$ is of class $\mathscr{C}^1$, with support in $[0, K]$ with $K > 0$. Using the result that $f'(t) \rightarrow 0$ when $t \rightarrow +\infty$, show that for all $\ell \geqslant 0$, $f(t+\ell) - f(t) \rightarrow 0$ when $t \rightarrow +\infty$.