A pile of coins is arranged in a square matrix, and there are more than 4 coins. If a layer is added to the vertical and horizontal sides of the square, there will be a shortage of 9 coins. How many coins are there in this pile?
一堆硬币排成正方形方阵，多余4枚．若正方形纵横两个方面各增加一层，则缺少9枚，问这堆硬币有多少枚？
<gadget id="calculator">4 + 9 + 1</gadget>
<output>14</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<gadget id="calculator">7 - 2</gadget>
<output>5</output>

<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<gadget id="calculator">25 + 4</gadget>
<output>29</output>

<result>29</result>