#!/bin/python3

import sys

def minimumNumber(n, password):
    # Return the minimum number of characters to make the password strong
    character_sets = ["0123456789", "abcdefghijklmnopqrstuvwxyz", "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "!@#$%^&*()-+"]
    missing = {s:True for s in character_sets}
    for x in password:
        for s in missing:
            if x in s:
                missing[s] = False
                break
    return max(sum(missing.values()), 6 - n)

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