One end of the road is 72 meters long. Originally, a flag was inserted every 4 meters (both ends) on one side of the road. Later, it was changed to be inserted every 6 meters. How many flags cannot be moved when re-inserted?
一端路长72米，原来在路的一侧每隔4米插一面旗(两端都插)，后来改为每隔6米插一面，重插时，有几面旗不能动？
<gadget id="calculator">72 / 12</gadget>
<output>6</output>

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

<result>7</result>