There are three weights of 1 gram, 2 gram and 4 gram, how many objects of different weights can be weighed in total.
有1克、2克、4克这三个砝码，一共可以称出多少种不同重量的物体．
<gadget id="calculator">3 + 3 + 1</gadget>
<output>7</output>

<result>7</result>