A student has a balance weight of 1 gram, 2 grams, 4 grams, and 8 grams in his hand. Put one or several weights on one end of the balance, and put the object on the other end of the balance to weigh. How many objects of different weights?
某同学手里有1克、2克、4克、8克的天平砝码各一个，将砝码一个或几个放在天平一端，将物体放在天平的另一端称量，最多可以称出多少种不同重量的物体．
<gadget id="calculator">4 + 6 + 4 + 1</gadget>
<output>15</output>

<result>15</result>