In a row of 12 girls, a boy is inserted between every two girls, how many boys should be inserted in total.
在一排12名的女生队伍中，每两名女生之间插进一名男生，一共要插进多少名男生．
<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<result>11</result>