The corridor of a dormitory is 15 meters long, with 6 colorful flags inserted at both ends of the corridor. According to this calculation, the corridor of the office building is 27 meters long, and how many colored flags should be planted.
一座宿舍的走廊长15米，插有6面彩旗，走廊两端都要插．照这样计算，办公大楼走廊长27米，要插多少面彩旗．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">27 / 3</gadget>
<output>9</output>

<gadget id="calculator">9 + 1</gadget>
<output>10</output>

<result>10</result>