use a helper column and check if second value is less than first value, if it is put first value at top of helper column otherwise put zero in top of helper column. Then check if third value of column 1 is less than second value, if it is, put secons value of column 1 otherwise zero.

Process whole list, total of helper column is the decreasing series total, total of column 1 MINUS total of column 2 is the increasing series total.