The original weights of 1 gram, 3 grams, 5 grams and 7 grams are each one. After losing one weight, it is no longer possible to weigh 9 grams and 12 grams at a time. How many grams of weights are lost?
原有1克、3克、5克和7克的砝码各一个，丢掉一个砝码后，再也无法一次称出9克、12克的重量，丢掉的是几克的砝码？
<result>5</result>