#!/bin/python3

import sys

def minimumNumber(n, password):
    # Return the minimum number of characters to make the password strong
    small = 0
    big = 0
    digit = 0
    special = 0
    num = 0
    for i in range(n):
        if ord(password[i]) >= 65 and ord(password[i]) <= 90:
            big += 1
        elif ord(password[i]) >= 97 and ord(password[i]) <= 122:
            small += 1
        elif ord(password[i]) >= 48 and ord(password[i]) <= 57:
            digit += 1
        else:
            special += 1
    if small == 0:
        num += 1
    if big == 0:
        num += 1
    if digit == 0:
        num += 1
    if special == 0:
        num += 1
    num = num if num >= 6-n else 6-n
    return num

if __name__ == "__main__":
    n = int(input().strip())
    password = input().strip()
    answer = minimumNumber(n, password)
    print(answer)