#!/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 = "!@#$%^&*()-+"
    
    digit=False
    lc=False
    uc=False
    sc=False
    
    req=4
    
    for char in password:
        if char in numbers:
            digit=True
        if char in lower_case:
            lc=True
        if char in upper_case:
            uc=True
        if char in special_characters:
            sc=True
            
    if digit==True:
        req-=1
    if lc==True:
        req-=1
    if uc==True:
        req-=1
    if sc==True:
        req-=1

    if len(password)>=6:
        return req
    return max(6-len(password),req)

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