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

public class Solution {

    private static final int INTEGER = 0;
    private static final int LOWER = 1;
    private static final int UPPER = 2;
    private static final int SPECIAL = 3;
    private static final String SPECIAL_STRING = "!@#$%^&*()-+";
    private static final String NUMBERS = "0123456789";
    private static final boolean[] HAS_ARRAY = new boolean[4];

    static int minimumNumber(int n, String password) {
        for (char ch : password.toCharArray()) {
            if (ch >= 'a' && ch <= 'z' && !HAS_ARRAY[LOWER]) {
                HAS_ARRAY[LOWER] = true;
            } else if (ch >= 'A' && ch <= 'Z' && !HAS_ARRAY[UPPER]) {
                HAS_ARRAY[UPPER] = true;
            } else if (SPECIAL_STRING.indexOf(ch) > -1) {
                HAS_ARRAY[SPECIAL] = true;
            } else if (NUMBERS.indexOf(ch) > -1) {
                HAS_ARRAY[INTEGER] = true;
            }
        }

        int toAdd = 4;
        for (boolean has : HAS_ARRAY) {
            if (has) {
                --toAdd;
            }
        }

        return Math.max(6 - password.length(), toAdd);
    }

    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();
    }
}