Add 7 to a number, multiply by 7, subtract 7, and finally divide by 7. The result is still 7. What is the number?
一个数加上7，再乘以7，又减去7，最后除以7，结果还是7，这个数是多少．
<gadget id="calculator">7 * 7</gadget>
<output>49</output>

<gadget id="calculator">49 + 7</gadget>
<output>56</output>

<gadget id="calculator">56 / 7</gadget>
<output>8</output>

<gadget id="calculator">8 - 7</gadget>
<output>1</output>

<result>1</result>