The students lined up in a square to perform radio exercises. Xiaohai's position is the 4th from the front, from the back, from the left, and from the right. How many students participated in the broadcasting exercise performance?
同学们排成一个方阵进行广播操表演．小海的位置从前、从后、从左、从右数都是第4个，参加广播操表演的共有多少个同学．
<gadget id="calculator">3 + 3 + 1</gadget>
<output>7</output>

<gadget id="calculator">7 * 7</gadget>
<output>49</output>

<result>49</result>