There are 4 pieces on each side of a square (one on each corner), how many pieces are there on the four sides?
一个正方形的每条边放有4枚棋子(每个角上各有1枚)，四条边上共有多少枚．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">16 - 4</gadget>
<output>12</output>

<result>12</result>