using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static int minimumNumber(int n, string password) {
        string numbers = "0123456789";
        string lower_case = "abcdefghijklmnopqrstuvwxyz";
        string upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        string special_characters = "!@#$%^&*()-+";
        bool[] allchars = {false, false, false, false};
        int char_varcount = 0;
        int char_count = 0;
        for(int i = 0; i < n; i++) {
            if(numbers.Contains(password[i])) {
                allchars[0] = true;
            }
            if(lower_case.Contains(password[i])) {
                allchars[1] = true;
            }
            if(upper_case.Contains(password[i])) {
                allchars[2] = true;
            }
            if(special_characters.Contains(password[i])) {
                allchars[3] = true;
            }
            else {
                continue;
            }
        }
        for(int i = 0; i < 4; i++) {
            if(!allchars[i]) {
                char_varcount++;
            }
        }
        if(password.Length < 6) {
                char_count = 6 - password.Length;
        }
        if(char_count > char_varcount) {
            return char_count;
        }
        else {
            return char_varcount;
        }
    }

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        string password = Console.ReadLine();
        int answer = minimumNumber(n, password);
        Console.WriteLine(answer);
    }
}