There are 1 gram, 2 gram, 4 gram, and 8 gram weights. Choose one or more weights and place them on the right side of the balance. How many objects with different masses can be weighed?
有1克、2克、4克和8克的砝码各一个，选择其中的一个或几个砝码，只能放在天平的右边，那么一共可以称出多少种不同质量的物体．
<gadget id="calculator">4 + 6 + 4 + 1</gadget>
<output>15</output>

<result>15</result>