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 special_characters = "!@#$%^&*()-+";

        Set<Integer> set= new HashSet<>();
        for(int i=0; i<n; i++){
            if(password.charAt(i)>='0' && password.charAt(i)<='9') set.add(0);
            else if(password.charAt(i)>='a' && password.charAt(i)<='z') set.add(1);
            else if(password.charAt(i)>='A' && password.charAt(i)<='Z') set.add(2);
            else if(special_characters.contains(String.valueOf(password.charAt(i)))) set.add(3);

        }
//        for(int i: set) System.out.println(i);
        int min=n<6?6-n:0;
        return Math.max(4-set.size(), min);
    }

    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();
    }
}