This sequent is not provable.\\

$\mathcal{M} : p = T, q = T, r = T, s = T$\\
$\mathcal{M} \models p \imp (q \lor r)$\\
$\mathcal{M} \models q \imp s$\\
$\mathcal{M} \models \neg(p \imp (q \land s))$
