There are 15 consecutive natural numbers, and each time a rectangle is used to frame 4 consecutive natural numbers, how many different ways are there in total?
有15个连续的自然数，每次用长方形框出4个连续的自然数，一共有多少种不同的框法．
<gadget id="calculator">15 - 4</gadget>
<output>11</output>

<gadget id="calculator">11 + 1</gadget>
<output>12</output>

<result>12</result>