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
        int lenNeed = (password.length()>6)?0:(6-password.length());
        int count = 0;
        String numbers = "0123456789";
        String lower_case = "abcdefghijklmnopqrstuvwxyz";
        String upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        String special_characters = "!@#$%^&*()-+";
        count += contains(password,numbers);
        count += contains(password,lower_case);
        count += contains(password,upper_case);
        count += contains(password,special_characters);
        return Math.max(4-count,lenNeed);
    }
    public static int contains(String src,String lib){
        for(char c: lib.toCharArray()){
            if(src.indexOf(c)!=-1) return 1;
        }
        return 0;
    }

    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();
    }
}