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 = "!@#$%^&*()-+";
        
        boolean[] has = new boolean[4];
        
        for (int i = 0; i < n && !(has[0] && has[1] && has[2] && has[3]); i++) {
            String c = "" + password.charAt(i);
            if (numbers.contains(c)) {
                has[0] = true;
            } else if (lower_case.contains(c)) {
                has[1] = true;
            }
            else if (upper_case.contains(c)) {
                has[2] = true;
            }
            else if (special_characters.contains(c)) {
                has[3] = true;
            }
        }
        
        int count = 0;
        for (boolean b : has) {
            if (!b) {
                count++;
            }
        }
        
        if (n <= 2) {
            return 6 - n;
        } else if (n < 6) {
            return Math.max(count, 6-n);
        }
        
        return count;
        
    }

    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();
    }
}