Lumpy - The Bus Driver

Lumpy is a bus driver. Today, the conductor is absent so Lumpy has to do the conductor's job as well. There are N creatures in the bus. Sometimes the creatures don't carry change and can't pay the exact amount of the fare. Each creature in the bus today has paid an amount greater than his/her fare. You are given information about the extra amount paid by each creature, by an array A of size N, whe