Use the four numbers 1, 2, 3, and 4 to form a multiplication formula of multiplying a three-digit number by a one-digit number, and the product obtained is the largest.
用1、2、3、4四个数字组成一个三位数乘一位数的乘法算式，所得到的积最大的多少．
<gadget id="calculator">321 * 4</gadget>
<output>1_284</output>

<result>1_284</result>