Untitled

def solution(stationsA, stationsB, stationsC, origin, destination):
  if origin in stationsA and destination in stationsA:
    return "A"
  elif origin in stationsB and destination in stationsB: 
    return "B"
  elif origin in stationsC and destination in stationsC:
    return "C"
  elif origin in stationsA and destination in stationsB:
    return "AB" 
  elif origin in stationsB and destination in stationsA:
    return "AB"
  elif origin in stationsB and destination in stationsC:
    return "BC"
  elif origin in stationsC and destination in stationsB: 
    return "BC" 
  elif origin in stationsA and destination in stationsC:
    return "ABC"
  elif origin in stationsC and destination in stationsA:
    return "ABC"
  else:
    return ""