kgv 12 20 == 60
kgv 15 40 == 120
kgv (-15) 40 == 120
kgv 17 0 == 0

agv 12 20 (50,130) == [60,120]
agv 15 40 ((-50),150) == [120]
agv (-15) 20 (60,180) == [60,120,180]
agv 15 40 (200,10) == []
agv 17 0 ((-1000),1000) == []

type PassName         = String
type FlightNumber     = Integer
type PlaceOfDeparture = String
type Destination      = String
type Airfare          = Integer
type Database         = [(PassName,FlightNumber,PlaceOfDeparture,Destination,Airfare)]

db = [ ("Anton",857,"Vienna","London",237),
       ("Berta",456,"Paris","Berlin",278),
       ("Anton",123,"Rome","London",417),
       ("Anton",109,"London","Berlin",237),
       ("Karla",888,"Vienna","Rome",350),
       ("Karla",832,"Rome","London",417),
       ("Berta",857,"Vienna","London",199),
       ("Karla",753,"Vienna","London",237) ]

flights db "Anton" == [(109,237),(123,417),(857,237)]
pass2Dest db "London" == ["Anton","Anton","Berta","Karla","Karla"]  
mostValuedPass db "Vienna" "London" == (["Karla","Anton"],237)