There are 2 gram, 5 gram and 7 gram weights, how many different masses can be combined by choosing one or several of them?
有2克、5克和7克的砝码各一个，选择其中的一个或几个，能组合多少种不同的质量？
<gadget id="calculator">3 + 2 + 1</gadget>
<output>6</output>

<result>6</result>