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[] numbers = new int[10];
        int[] lower_case = new int[26];
        int[] upper_case = new int[26];
        
        String special_characters = "!@#$%^&*()-+";
        Map<Character, Integer> special_char = new HashMap<>();
        
        for(char c:special_characters.toCharArray()){
            special_char.put(c, 0);
        }
        
        boolean number_flag = false, lower_case_flag = false, upper_case_flag = false, special_case_flag = false;
        
        for(char c:password.toCharArray()){
            if( c >= '0' && c <= '9'){
                number_flag = true;
                numbers[c - '0']++;
            }
            else if( c >= 'a' && c <= 'z'){
                lower_case_flag = true;
                lower_case[c - 'a']++;
            }
            else if( c >= 'A' && c <= 'Z'){
                upper_case_flag = true;
                upper_case[c-'A']++;
            }
            else if(special_char.containsKey(c)){
                special_case_flag = true;
                special_char.put(c, special_char.get(c)+1);
            }
        }
        
        int k = 0;
        if(n < 6){
            if(!number_flag) k++;
            if(!lower_case_flag) k++;
            if(!upper_case_flag) k++;
            if(!special_case_flag) k++;
            if( n + k >= 6) return k;
            else return k + 6 - (n+k);
        }
        else{
            if(!number_flag) k++;
            if(!lower_case_flag) k++;
            if(!upper_case_flag) k++;
            if(!special_case_flag) k++;
        }
        return k;
    }

    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();
    }
}