!$ S \, = \, C \, \cdot \, A \, + \, \bar{D} \, \cdot \, C \, \cdot \, \bar{B} \, \cdot \, \bar{A} \, + \, \bar{D} \, \cdot \, \bar{C} \, \cdot \, B \, \cdot \, A \, + \, D \, \cdot \, C \, \cdot \, B \, \cdot \, \bar{A} \, + \, D \, \cdot \, \bar{C} \, \cdot \, \bar{B} \, \cdot \, A !$