numbers = list("0123456789")
lower_case = list("abcdefghijklmnopqrstuvwxyz")
upper_case = list("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
special_characters = list("!@#$%^&*()-+")


s = int(raw_input())
word = raw_input()

word_set = set(list(word))

has_char = [False,False,False,False]

for char in word_set:
  if char in numbers:
    has_char[0] = True
  elif char in lower_case:
    has_char[1] = True
  elif char in upper_case:
    has_char[2] = True
  elif char in special_characters:
    has_char[3] = True
    
changes = has_char.count(False)
new_len = len(word) + changes
    
if new_len < 6:
  print 6 - new_len + changes
else:
  print changes