□/●=6…7, the minimum number to be filled in □
□/●=6…7，□里最小要填多少
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<gadget id="calculator">6 * 8</gadget>
<output>48</output>

<gadget id="calculator">48 + 7</gadget>
<output>55</output>

<result>55</result>