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 = "!@#$%^&*()-+";
        int[] flags = new int[4];
        HashSet<Character> set = new HashSet<>();
        for(int i = special_characters.length() - 1; i >= 0; --i){set.add(special_characters.charAt(i));}
        char ch = ' ';
        for(int i = 0; i < n; ++i){
            ch = password.charAt(i);
            if('0' <= ch && ch <= '9'){
                flags[0] |= 1;
            }else if('a' <= ch && ch <= 'z'){
                flags[1] |= 1;
            }else if('A' <= ch && ch <= 'Z'){
                flags[2] |= 1;
            }else if(set.contains(ch)){
                flags[3] |= 1;
            }
        }
        int sum = 0;
        for(int i = 0; i < 4; ++i) sum += flags[i];
        sum = 4 - sum + n;
        return Math.max(6 - n, sum - n);
    }

    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();
    }
}