Adding 9 students to a square array of students can turn the original square array into a large square array with one more row and one more column, so how many students are there in the original square array.
在一个学生方阵中加入9人，可将原来的方阵变成一个多一行，多一列的大方阵，则原来的方阵有学生多少人．
<gadget id="calculator">9 + 1</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<result>16</result>