: 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>8 1</span></div></code></pre></div><h4>样例输出</h4><div class="ui existing segment"><pre style="margin-top:0; margin-bottom:0;"><code class="lang-plain">
			<div class=content><span class=sampledata>8.00000<br />
<br />
<br />
【数据规模和约定】<br />
	100%的数据满足1 ≤ N ≤ 200, 1 ≤