There are three weights of different weights, namely 1 gram, 4 grams, and 9 grams. How many items of different weights can be weighed on the balance with only these brick weights?
有三种不同重量的砝码，分别是1克、4克、9克，仅用这些砖码可在天平上称出多少种不同重量的物品．
<result>11</result>