n> <span class="identifier">M3</span>
                                   <span class="special">---+--------</span>            <span class="special">---+---------------------------</span>
                                   <span class="identifier">e</span>  <span class="special">|</span>     <span class="identifier">s</span> <span class="identifier">m</span>            <span class="identifier">e</span>  <span class="special">|</span>             <span class="identifier">S1</span> <span class="identifier">S2<