#!/bin/python

import sys

def minimumNumber(n, password):
    # Return the minimum number of characters to make the password strong
    numbers = "0123456789"
    lower_case = "abcdefghijklmnopqrstuvwxyz"
    upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    special_characters = "!@#$%^&*()-+"
    b,l,u,s,re,ru=[0,0,0,0,0,0]
    for letter in password:
        if letter in numbers:
            b=1
        if letter in lower_case:
            l=1
        if letter in upper_case:
            u=1
        if letter in special_characters:
            s=1
    if (b+l+u+s)<=4:
        ru=4-(b+l+u+s)
    if n<6:
        re=6-n
    
    return max(re,ru)

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