1. Given that the function $f(x)$ is a decreasing function on $\mathbf{R}$, and it is an odd function. If $m, n$ satisfy the inequality system $\left\{\begin{array}{l}f(m)+f(n-2) \leqslant 0, \\ f(m-n-1) \leqslant 0,\end{array}\right.$ then the range of $5 m-n$ is $\qquad$ .
The original inequality is equivalent to $\left\{\begin{array}{l}m+n-2 \geqslant 0, \\ m-n-1 \geqslant 0,\end{array}\right.$ Combining the feasible region, we get $z=5 m-n \geqslant 7$, so the range of $5 m-n$ is $[7,+\infty)$.