class="row"><div class="column"><h4 class="ui top attached block header">输出格式</h4><div class="ui bottom attached segment font-content"><div style="position: relative; overflow: hidden;"><div class=content><div>&nbsp;</div>
<div><span style="font-size: medium">　　共一行，即集合S，<span style="color: #ff0000">每个区间后面带一个空格</span>。若S为空则输出&quot;empty set&quot;。</span></div>
<div><span style="font-size: medium">&nbsp;</span></div></div></div></div></div></