There were 5 weights of 1 gram, 2 gram, 4 gram, 8 gram and 16 gram, but now one of them is lost, so the weights of 12 gram and 23 gram cannot be weighed. How many grams of weight are missing.
原有1克、2克、4克、8克、16克5个砝码，现丢失了其中的一个，因而12克和23克的重量都不能称了．丢失的是多少克的砝码．
<result>4</result>