#!/bin/python3

import sys

def minimumNumber(n, password):
    # Return the minimum number of characters to make the password strong
    nreqs = 0
    hasNum = hasLC = hasUC = hasSC = False
    
    special_characters = list("!@#$%^&*()-+")
    
    for c in list(password):
        if c.isnumeric():
            hasNum = True
        elif c.isalpha() and c.islower():
            hasLC = True
        elif c.isalpha() and c.isupper():
            hasUC = True
        elif c in special_characters:
            hasSC = True
            
    if hasNum is True:
        nreqs += 1
    if hasLC is True:
        nreqs += 1
    if hasUC is True:
        nreqs += 1
    if hasSC is True:
        nreqs += 1
    return max(4 - nreqs, 6 - len(password))

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