$\forall$$A$:Type, ${\it op}$:($A$$\rightarrow$$A$$\rightarrow$$A$), ${\it id}$:$A$, $p$, $q$:$\mathbb{Z}$, $E$:(\{$p$..$q$$^{-}$\}$\rightarrow$$A$). $\Pi$(${\it op}$,${\it id}$) $p$ $\leq$ $i$ $<$ $q$. $E$($i$) $\in$ $A$