Days the feed never delivered

Each source is supposed to land once a day. Before anyone trusts a monthly total, they want the days that never arrived.

Input

loads source string -- 'orders', 'returns', ... load_date string -- 'YYYY-MM-DD'

A source can land twice on one day. A day it missed has no row at all, which is the whole problem.

Output

One row per missing day per source:

source
missing_date — 'YYYY-MM-DD'

A day is missing when it falls between that source's earliest and latest load and has no row. Report nothing outside that range — before a source's first load it did not exist yet, and after its last there is nothing to say.

Example

source	missing_date
orders	2024-01-02

Constraints

Every missing day, not the first one. A four-day silence is four rows.
Sources are independent, and their ranges differ.
Two loads on one day are one delivered day, not a duplicate.
A source that never missed a day contributes no rows. An empty result is a correct answer.
Row order is not graded. Column names and their order are.

Community-reported interview topic. Not an official company question and no affiliation is implied.