Students line up to do exercises, with the same number of people in each row. Xiao Ming's position is the 5th from the left, the 4th from the right, the 3rd from the front, and the 7th from the back. How many students do exercises?
同学们排队做操，每行人数同样多，小明的位置从左数起是第5个，从右数起是第4个，从前数起是第3个，从后数起是第7个．做操的同学共有多少个．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">3 + 6</gadget>
<output>9</output>

<gadget id="calculator">8 * 9</gadget>
<output>72</output>

<result>72</result>