Xiao Ming participates in a group gymnastics performance, and he is in the middle of a phalanx. Counting from the front, from the back, from the left, and from the right, he is always the 7th. How many people participated in the group gymnastics performance?
小明参加集体操表演，排在一个方阵队伍中间，从前、从后、从左、从右开始数他都是站在第7位，参加集体操表演的共有多少人．
<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">14 - 1</gadget>
<output>13</output>

<gadget id="calculator">13 * 13</gadget>
<output>169</output>

<result>169</result>