There are number cards 1-4 each, and any cards are taken out from them and placed on the table, how many different numbers can be formed at most.
有数字卡片1-4各一张，从中任意取出卡片放在桌面上，最多能组成多少个不同的数．
<gadget id="calculator">4 * 1</gadget>
<output>4</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">4 * 3 * 2</gadget>
<output>24</output>

<gadget id="calculator">4 * 3 * 2 * 1</gadget>
<output>24</output>

<gadget id="calculator">4 + 12 + 24 + 24</gadget>
<output>64</output>

<result>64</result>