# Requirement change

Groups keep telling us the same thing: at the end of a trip, three people don't want to make six
separate payments to settle up when two would do. Right now the app can only tell you what one
person owes another. We want it to be able to look at the whole group at once and suggest the
smallest number of payments that would leave everyone square.

The classic case: Amir fronted a meal that Bela owed him for, and separately Bela fronted
something that Chen owed her for. Right now, that's two debts — Amir is owed by Bela, Bela owes
Chen — er, sorry, the other way round, but you get the idea. The point is Bela is stuck in the
middle owing and being owed the same amount, and there's no reason for that money to actually
pass through her hands. The app should be able to say "Chen, just pay Amir directly" instead.

A few things to be clear about:

- **This is a suggestion, not an action.** Asking for the settlement plan should not move any
  balance. Somebody still has to actually pay, and record it the normal way, for anything to
  change.
- **It has to add up.** If every suggested payment happened, everybody would end up owing nothing
  and being owed nothing.
- **Somebody who's already square shouldn't appear in the plan at all** — there's nothing for them
  to pay or receive.
- We are not asking for a specific algorithm or a specific tie-break when there's more than one
  equally good way to do it. We just want the fewest payments.
