It simulates elevators of building by telling people which elevator to choose.
Our building will have elevators from A to F. All the elevators will be at the first floor of the building at the beginning of the day.
For each person our app will provide letter of elevator and approximate arrival time of elevator.
Elevator passes one floor in 4 seconds.
Input: 1 >> 5 @ 0, 1 >> 6 @ 2, 5 >> 6 @ 12, 6 >> 7 @ 20
Output: A, B, C, A