3□9*3 If the product is a three-digit number, what is the maximum number in □.
3□9*3要使积是三位数，□里最大填多少．
<gadget id="calculator">0 * 3</gadget>
<output>0</output>

<gadget id="calculator">0 + 2</gadget>
<output>2</output>

<result>2</result>