import sys
numbers = "0123456789"
lower_case = "abcdefghijklmnopqrstuvwxyz"
upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
special_characters = "!@#$%^&*()-+"
n = input()
s = raw_input()
ans = max(0, 6 - n)
upper, lower, num, special = 0, 0, 0, 0
for i in range(n):
    for j in range(0, len(numbers)):
        if numbers[j] == s[i]:
            num = 1
    for j in range (len(special_characters)):
        if special_characters[j] == s[i]:
            special = 1
    for j in range(0, len(lower_case)):
        if lower_case[j] == s[i]:
            lower = 1
    for j in range(0, len(upper_case)):
        if upper_case[j] == s[i]:
            upper = 1
ans = max(ans, 4 - (lower + upper + special + num))
print ans