#!/bin/python3

import sys

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

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