Volunteer Audit Window Shift Average

A community-service nonprofit runs a rolling 30-day audit before certifying volunteers for a service award. Every time a volunteer checks in for a shift, the system logs the volunteer's ID, the shift's ID, and the calendar date -- sometimes the same check-in gets logged more than once by mistake. For a given audit window (a fixed end date together with the 29 days immediately before it, 30 calendar days total, inclusive on both ends), a volunteer counts as "active" if at least one of their logged entries falls inside that window. For every active volunteer, the nonprofit wants the number of distinct shift IDs they logged inside the window, and then the average of that count across all active volunteers.

Input format

• Line 1: the audit end date, in the format YYYY-MM-DD.
• Line 2: an integer n (0 <= n <= 100000), the number of log entries.
• Each of the next n lines contains three space-separated tokens: volunteerId shiftId date, where volunteerId and shiftId are integers (1 <= value <= 1000000000) and date is in the format YYYY-MM-DD. All dates are valid calendar dates between the years 2000 and 2100 inclusive.

Output format

Print a single value: the average number of distinct shifts logged by each active volunteer over the 30-day window ending on (and including) the audit end date and beginning 29 days earlier (inclusive) -- rounded to exactly two decimal places using round-half-up rounding. If there are no active volunteers, print 0.00.

Constraints

• 0 <= n <= 100000
• 1 <= volunteerId, shiftId <= 1000000000
• All dates are valid and given in YYYY-MM-DD format.

2019-07-27
14
1 1 2019-07-20
1 1 2019-07-20
1 1 2019-07-20
2 4 2019-07-20
2 4 2019-07-21
2 4 2019-07-21
3 2 2019-07-21
3 2 2019-07-21
3 2 2019-07-21
3 5 2019-07-21
3 5 2019-07-21
3 5 2019-07-21
4 3 2019-06-25
4 3 2019-06-25

1.33

2020-01-01
1
5 10 2019-01-01

0.00