#!/bin/python

import sys

def minimumNumber(s):
    numbers = "0123456789"
    lower_case = "abcdefghijklmnopqrstuvwxyz"
    upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    special_characters = "!@#$%^&*()-+"
    c = [False] * 4
    for ch in s:
        if ch in numbers:
            c[0] = True
        if ch in lower_case:
            c[1] = True
        if ch in upper_case:
            c[2] = True
        if ch in special_characters:
            c[3] = True
    n = 4
    for bo in c:
        if bo:
            n -= 1

    if n > 6 - len(s):
        print (n)
    else:
        print(6 - len(s))


if __name__ == "__main__":
    n = int(raw_input().strip())
    password = raw_input().strip()
    minimumNumber(password)