$\forall$$x$:Id, $t$, $v$:Top, $x_{1}$:Id, $t_{1}$, $v_{1}$:Top.
\\[0ex]$\neg$$x$ $=$ $x_{1}$ $\Rightarrow$ ($x$ : $t$ initially $x$ = $v$ $\Vert\!+$ $x_{1}$ : $t_{1}$ initially $x_{1}$ = $v_{1}$)