If a box of Go pieces is used to form a solid square matrix, there are 7 more pieces; if 8 pieces are added, one piece can be added on each side to form a large solid square matrix. How many chess pieces are there in this box?
用一盒围棋子排成一个实心方阵，则多7粒；如果再增加8粒，每边就可以增加一粒成为一个大的实心方阵．这盒围棋子共有多少粒．
<gadget id="calculator">7 + 8 + 1</gadget>
<output>16</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">8 * 8</gadget>
<output>64</output>

<gadget id="calculator">64 - 8</gadget>
<output>56</output>

<result>56</result>