#!/bin/python

import sys

numbers = "0123456789"
lower_case = "abcdefghijklmnopqrstuvwxyz"
upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
special_characters = "!@#$%^&*()-+"

def minimumNumber(n, password):
    
    num, low, upp, spec = False, False, False, False
    for l in password :
        if l in numbers : num = True
        elif l in lower_case : low = True
        elif l in upper_case : upp = True
        else : spec = True
            
    add = [num,low,upp,spec].count(False)
    
    if n+add < 6 : return 6-n
    else : return add

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