Three people A, B and C run an 800-meter race along a 400-meter circular track. When A runs 1 lap, B runs (1/7) more laps than A. C runs (1/7) laps less than A. If their respective running speeds are always the same, then when B reaches the finish line, how many meters is A in front of C?
甲、乙和丙三人沿着400米环形跑道进行800米跑比赛，当甲跑1圈时，乙比甲多跑(1/7)圈．丙比甲少跑(1/7)圈．如果他们各自跑步的速度始终不变，那么，当乙到达终点时，甲在丙前面多少米处．
<gadget id="calculator">700 - 600</gadget>
<output>100</output>

<result>100</result>