def FINDMOST(S):
  COUNT = {}
  for CHAR in S:
    if CHAR in COUNT:
      COUNT[CHAR] += 1
    else:
      COUNT[CHAR] = 1
  MAXIMUM = max(COUNT.values())
  MOSTCHRS = [CHAR for CHAR, COUNTI in COUNT.items() if COUNTI == MAXIMUM]
  return list(sorted(MOSTCHRS))
Q = oct(int(input(), 16))[2:]
print(*FINDMOST(Q))