A large shark has a tail half as long as its body and a head half as long as its tail. Given that the head is 3 meters long, what is the total length of this big shark in meters?
一条大鲨鱼，尾长是身长的一半，头长是尾长的一半．已知头长3米，这条大鲨鱼全长多少米．
<gadget id="calculator">3 * 2 * 2</gadget>
<output>12</output>

<result>12</result>