$\forall$${\it es}$:ES, $L$:(Id List).
\\[0ex]fischer($L$) $\Rightarrow$ ($\forall$$e_{1}$, $e_{2}$:E. Try($e_{1}$) $\Rightarrow$ Try($e_{2}$) $\Rightarrow$ $e_{1}$ $<$f $e_{2}$ $\Rightarrow$ ($e_{1}$ $<$ $e_{2}$))