sales has columns store, date (datetime) and amount.

Sorted by date within each store, add a cumulative column holding the running total of that store's amounts. Return the original columns plus cumulative, sorted by store then date, with the index renumbered from 0. The running total must restart at each store rather than carrying over.

Input

  store       date  amount
0     A 2022-01-03    30.0
1     A 2022-01-01    10.0
2     A 2022-01-02    20.0
3     B 2022-01-02     7.0
4     B 2022-01-01     5.0

Output

  store       date  amount  cumulative
0     A 2022-01-01    10.0        10.0
1     A 2022-01-02    20.0        30.0
2     A 2022-01-03    30.0        60.0
3     B 2022-01-01     5.0         5.0
4     B 2022-01-02     7.0        12.0