#!/bin/python

import sys

def minimumNumber(n, password):
    # Return the minimum number of characters to make the password strong
    numbers = "0123456789"
    lower_case = "abcdefghijklmnopqrstuvwxyz"
    upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    special_characters = "!@#$%^&*()-+"
    p=password
    nf=0
    uf=0
    lf=0
    sf=0
    for i in range(n):
        if p[i] in numbers:
            nf=1
        elif p[i] in lower_case:
            lf=1
        elif p[i] in upper_case:
            uf=1
        else:
            sf=1
            
    if n<6:
        print max(6-n,4-lf-uf-sf-nf)
    else:
        print 4-lf-uf-sf-nf
        

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