The naughty room is 3.5 meters long, 3 meters long and 3 meters wide. Excluding the doors and windows of 6.5m**2, the walls and roof of the room are covered with wallpaper. How much wallpaper does this room need at least?
淘气的房间长3.5米，长3米，宽3米．除去门窗6.5m**2，房间墙壁和房顶都贴上墙纸，这个房间至少需要多大的墙纸？
<gadget id="calculator">3.5 * 3</gadget>
<output>10.5</output>

<gadget id="calculator">3.5 * 3 * 2</gadget>
<output>21</output>

<gadget id="calculator">3 * 3 * 2</gadget>
<output>18</output>

<gadget id="calculator">18 - 6.5</gadget>
<output>11.5</output>

<gadget id="calculator">10.5 + 21 + 11.5</gadget>
<output>43</output>

<result>43</result>