��总和，在一条直线上继续行进不用转弯。每一段 跑道都是可以双向行驶的。</p>
<p></p></div></div></div></div><div class="row"><div class="column"><h4 class="ui top attached block header">输入格式</h4><div class="ui bottom attached segment font-content"><div style="position: relative; overflow: hidden;"><div class=content><p>Oneline with 3 &lt; =&nbsp; N &lt; =&nbsp; 10000{the number of nodes{and N &lt; =&nbsp; M &lt; =&nbsp; 2N {the number<br />
of edges.<br />
N lines wi