#!/bin/python

import sys

def minimumNumber(n, password):
    numbers = "0123456789"
    lower_case = "abcdefghijklmnopqrstuvwxyz"
    upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    special_characters = "!@#$%^&*()-+"
    add = [True, True, True, True]
    for i in range(len(numbers)):
        num = numbers[i]
        if num in password:
            add[0] = False
    for i in range(len(lower_case)):
        lc = lower_case[i]
        if lc in password:
            add[1] = False
    for i in range(len(upper_case)):
        uc = upper_case[i]
        if uc in password:
            add[2] = False
    for i in range(len(special_characters)):
        uc = special_characters[i]
        if uc in password:
            add[3] = False
    ans = 0
    for i in add:
        if i:
            ans+=1
    if len(password) + ans < 6:
        ans = 6 - len(password)
    return ans
if __name__ == "__main__":
    n = int(raw_input().strip())
    password = raw_input().strip()
    answer = minimumNumber(n, password)
    print answer