pan class="special">|</span> <span class="identifier">S</span> <span class="identifier">S</span>     <span class="identifier">S</span>      
                                   <span class="identifier">m</span>  <span class="special">|</span> <span class="identifier">m</span> <span class="identifier">m</span> <span class="identifier">m</span> <span class="identifier">m</span>            <span class="identifier">M</span>  <span class="special">|</span> <span class="identifier">M</span> <span class="identifier