span><span class="ss">v</span><span class="w">                       </span><span class="ss">v</span><span class="w">                       </span><span class="ss">v</span><span class="w">
  </span><span class="o">+</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">--</span><span class="o">+</span><span class="w">    </span><span class="o