一根铁丝，用去它的https://bgk-photo.cdn.bcebos.com/doc/pic/item/1b4c510fd9f9d72aad215f16dc2a2834349bbb70.jpg是12米，如果用去它的https://bgk-photo.cdn.bcebos.com/doc/pic/item/2f738bd4b31c87013086fded2f7f9e2f0708ff8d.jpg，那么还剩______米．