s="identifier">i</span>  <span class="special">|</span>    <span class="identifier">i</span>        <span class="identifier">S1</span> <span class="identifier">S2</span> <span class="identifier">S3</span> <span class="identifier">M1</span> <span class="identifier">M3</span>
                                   <span class="identifier">s</span>  <span class="special">|</span> <span class="identifier">s</span>   <span class="identifier">s</span> <span class="identifier">m</span>            <span class="identifi