pan class="identifier">b</span> <span class="identifier">p</span> <span class="identifier">S</span> <span class="identifier">M</span>
                                   <span class="special">---+--------</span>            <span class="special">---+------------</span>
                                    <span class="identifier">s</span> <span class="special">|</span> <span class="identifier">s</span>   <span class="identifier">s</span>               <span class="identifier">S</span> <span class="special">|</