Xiao Ming formed a solid square array with chess pieces, and later he added 11 more chess pieces, adding a row horizontally and vertically, forming a large solid square array. How many chess pieces are there in the original solid square?
小明用棋子摆成了一个实心方阵，后来他又加上了11个棋子，使横竖各增加了一排，成为一个大的实心方阵．原来的实心方阵有多少个棋子？
<gadget id="calculator">11 + 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 - 11</gadget>
<output>25</output>

<result>25</result>