pan> <span class="identifier">S2</span> <span class="identifier">S3</span> <span class="identifier">M1</span> <span class="identifier">M3</span>
<span class="special">---+----</span>                <span class="special">---+---------------</span>
<span class="identifier">s</span>  <span class="special">|</span> <span class="number">1</span>                  <span class="identifier">S1</span> <span class="special">|</span> <span class="number">1</span>  <span class="number">1</span>  <span class="number">1</