<span style="font-family:宋体;">【问题描述】</span> 

<span style="font-family:宋体;">找规律：根据下列规律找出第</span><span>N</span><span style="font-family:宋体;">个数是多少？</span><span> 1,2,3,5</span><span style="font-family:宋体;">……（</span><span>3&lt;=n&lt;=20</span><span style="font-family:宋体;">）</span> 

<span></span>

<span style="font-family:宋体;">【输入格式】</span> 

<span style="font-family:宋体;">一个正数数</span><span>n</span><span style="font-family:宋体;">（</span><span>3&lt;=n&lt;=20</span><span style="font-family:宋体;">）</span> 

<span style="font-family:宋体;">【输出格式】</span> 

<span style="font-family:宋体;">输出一个正整数</span><span> </span>

<span style="font-family:宋体;">【输入样例】</span> 

<span>5</span> 

<span style="font-family:宋体;">【输出样例】</span> 

<span>8</span> 

<span style="font-family:宋体;">【数据规模】</span> 

<span>3&lt;=n&lt;=20</span> 

<span style="font-family:宋体;">【时间限制】</span> 

<span>1s</span>