$\forall$$A$:Type, $f$:($A$$\rightarrow\mathbb{Z}$), $L$:$A$ List. 0$<\parallel$$L$$\parallel$ $\Rightarrow$ ($\exists$$a$$\in$$L$.$\forall$$x$$\in$$L$. $f$($x$)$\leq$$f$($a$))