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) {
      String  numbers = "0123456789";
    String lower_case = "abcdefghijklmnopqrstuvwxyz";
    String upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    String special_characters = "!@#$%^&*()-+";
            int[] flag=new int[4];
        for(int i=0;i<n;i++){
            String c=Character.toString(password.charAt(i));
            if(numbers.contains(c))
                flag[0]=1;
            else if(lower_case.contains(c))
                flag[1]=1;
            else if(upper_case.contains(c))
                flag[2]=1;
            else if(special_characters.contains(c))
                flag[3]=1;
        }
        int max=0;
        for(int i=0;i<4;i++){
            max+=flag[i];
        }
            
        return Math.max(4-max,6-n);
        // Return the minimum number of characters to make the password strong
    }

    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();
    }
}