There are 1 gram, 2 gram, and 4 gram weights. Choose one or several of them. How many objects with different masses can be directly weighed on the balance.
有1克、2克、4克的砝码各一个，选择其中的一个或几个，能在天平上直接称出多少种不同的质量的物体．
<gadget id="calculator">1 + 2 + 4</gadget>
<output>7</output>

<result>7</result>