31. 设min{a,b}={a,a⩽bb,a>bmin\left\{{a,b}\right\}=\left\{{\left.\begin{array}{l}{a,a\leqslant b}\\ {b,a>b}\end{array}\right.}\right.min{a,b}={a,a⩽bb,a>b，若函数f(x)=min{ex−1−xf(x)=min\{e^{x-1}-xf(x)=min{ex−1−x，−x2+2mx−1}-x^{2}+2mx-1\}−x2+2mx−1}有且只有三个零点，则实数mmm的取值范围为((( )))