import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static int minimumNumber(int n, String password) {
        // Return the minimum number of characters to make the password strong
        String numbers = "0123456789";
        String lower_case = "abcdefghijklmnopqrstuvwxyz";
        String upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        String special_characters = "!@#$%^&*()-+";
        int a = 0, b =0, c =0, d= 0;
        for(int i =0; i < password.length();i++){
            char ch = password.charAt(i);
            if(numbers.indexOf(ch) != -1){
                a = 1;
            }
            if(lower_case.indexOf(ch) != -1){
                b = 1;
            }
            if(upper_case.indexOf(ch) != -1){
                c = 1;
            }
            if(special_characters.indexOf(ch) != -1){
                d = 1;
            }
        }
        return 4-a-b-c-d > 6-password.length() ? 4-a-b-c-d : 6-password.length();
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        String password = in.next();
        int answer = minimumNumber(n, password);
        System.out.println(answer);
        in.close();
    }
}