There are 1 gram, 2 gram, 4 gram and 8 gram each, and one of them is lost, so the weight of 12 gram and 7 gram cannot be weighed. How much is the lost weight in gram?
有1克、2克、4克和8克的砝码各一个，其中丢了一个砝码，所以无法称出12克和7克的重量，问所丢的那个砝码是多少克重的？
<result>4</result>