There are 20 lottery tickets with consecutive numbers left at the lottery retail outlet. Uncle Li wants to buy 5 lottery tickets with consecutive numbers. How many different ways are there to buy them?
彩票零售点还剩20张连号彩票，李叔叔要买5张连号的彩票，一共有多少种不同的买法．
<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<gadget id="calculator">15 + 1</gadget>
<output>16</output>

<result>16</result>