#!/bin/python3

import sys

def minimumNumber(n, password):
    numbers = "0123456789"
    lower_case = "abcdefghijklmnopqrstuvwxyz"
    upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    special_characters = "!@#$%^&*()-+"
    
    flags = [0] * 4
    for i in password:
        if i in numbers:
            flags[0] += 1
        elif i in lower_case:
            flags[1] += 1
        elif i in upper_case:
            flags[2] += 1
        elif i in special_characters:
            flags[3] += 1
            
    cnt = 0
    for i in flags:
        if i == 0:
            cnt += 1
            
    return max(6 - len(password), cnt)

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