Surround a circle with 21 students whose student numbers are No. 1 to No. 21 in Class 3 and Class 1, and record the difference between the student numbers of all two adjacent students by reducing the difference. Then the 21 differences recorded What is the maximum value of the sum of values.
把三1班学号分别为1号到21号的21个同学围城一个圆圈，将所有相邻两个同学的学号以大减小所得的差值记录下来，那么记下的这21个差值的总和的最大值是多少．
<result>220</result>