Russian forest fires have been extinguished by various methods, one of which is to open up isolation zones, that is, to cut down trees in a strip-shaped area and clear them into open spaces for complete isolation. Assume that a fire source in a certain forest spreads to the surroundings at a speed of 10 m/min. The fire brigade immediately receives the notification and prepares to open a isolation zone within 1 hour to isolate the fire source. How many meters is the minimum length of this isolation zone (taken by π 3.14).
俄罗斯森林大火在扑灭时采用了多种方法，其中有一种是开辟隔离带，即砍掉一带状区域的树木并清理成空地，用于彻底隔离．假定现在某森林有一火源以10米/分的速度向四周蔓延，消防队马上接通知，准备在1小时内开辟好隔离带以隔离火源，请问这条隔离带至少有多少米(π取3.14)．
<gadget id="calculator">10 * 60</gadget>
<output>600</output>

<gadget id="calculator">2 * 3.14 * 600</gadget>
<output>3_768</output>

<result>3_768</result>