There are 1, 2, 4, 5, and 7 grams of weights each, and one of the weights is missing, so the balance cannot weigh 10 grams (the weight must be placed on one side of the balance). How many grams does the missing weight weigh?
有1、2、4、5、7克的砝码各1个，丢失了其中一个砝码，结果天平无法称出10克的重量(砝码必须放在天平的一边)．丢失的砝码重多少克．
<result>1</result>