��Ans，表示所求的方案数。</p></div></div></div></div></div><div class="row"><div class="column"><h4 class="ui top attached block header">样例</h4><div class="ui bottom attached segment font-content"><div style="position: relative; overflow: hidden;"><h4>样例输入</h4><div class="ui existing segment"><pre style="margin-top:0; margin-bottom:0;"><code class="lang-plain">
			<div class=content><span class=sampledata>6<br />
1 2<br />
2 3<br />
2 4<br />
4 5<br />
5 6</span></div></code></pre