Mary has 6 cards, and each card has a natural number greater than 0 written on it. After she selected 3 cards, she calculated the sum of them, she selected another 3 cards, and then calculated the sum of these 3 cards..., made 20 possible choices of 3 cards, and then calculated, and found that there are The sum of 10 kinds is equal to 16, and the sum of the other 10 kinds is equal to 18. So what is the smallest number among these cards
玛丽有6张卡片，每张卡片上都写有一个大于0的自然数．她选取了3张卡片后，算出了它们的总和，她又选另外3张卡片，再算出这3张卡片上的总和…，进行了可能的20种3张卡片的选择，然后计算，发现有10种总和等于16，另10种总和等于18．那么这些卡片中最小的数是多少
<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">16 - 12</gadget>
<output>4</output>

<result>4</result>