There are a bunch of chess pieces arranged in an n*n square matrix, and there are 3 extra chess pieces; if one row is added to the square matrix in both horizontal and vertical directions, 8 chess pieces are missing. Then how many pieces are there in this pile.
有一堆棋子，排列成n*n的正方形方阵，多余出3只棋子；如果在这个正方形方阵横纵两个方向各增加一行，则缺少8只棋子．则这堆棋子有多少只．
<gadget id="calculator">3 + 8 + 1</gadget>
<output>12</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 * 6</gadget>
<output>36</output>

<gadget id="calculator">36 - 8</gadget>
<output>28</output>

<result>28</result>