span>
<span class="identifier">m</span>  <span class="special">|</span>   <span class="number">1</span>                <span class="identifier">S2</span> <span class="special">|</span> <span class="number">1</span>  <span class="number">1</span>  <span class="number">1</span>
                        <span class="identifier">S3</span> <span class="special">|</span> <span class="number">1</span>  <span class="number">1</span>  <span class="number">1</span>
                        <span class="identifier">M1</