Courier slots

Choose which parcels a courier delivers to earn the most in fees.

A courier makes at most one delivery per day, on days numbered 1, 2, 3, .... Each parcel in parcels is a pair [last_day, fee]: the parcel can be delivered on any one day from day 1 up to and including last_day, and delivering it earns fee. A parcel that is not delivered earns nothing. Each parcel can be delivered at most once, and the courier may skip days.

The courier does not work on closed_days (road closures, holidays): no delivery can happen on those days, but they still count as days in the calendar, so a parcel's last_day is a calendar day even when it falls on a closure.

Input: parcels, a list of [last_day, fee] pairs of positive integers, and closed_days, a list of distinct positive integers in increasing order.

Output: an integer, the largest total fee the courier can earn. If there are no parcels, or none can be delivered, return 0.

Deadlines can be as large as a billion and there can be hundreds of parcels, so trying every selection of parcels will be too slow.