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 numbers = "0123456789", 
            lower_case = "abcdefghijklmnopqrstuvwxyz" , 
            upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" ,
            special_characters = "!@#$%^&*()-+";
        int count = 0;
        boolean l_c = false, u_c = false, no= false, sp=false;
        for(int i =0; i<n;i++){
            if(!l_c || !u_c || !no || !sp){
                Character ch = password.charAt(i);
                String tmp = String.valueOf(ch);
                if(!l_c && lower_case.contains(tmp)){
                    count++;
                    l_c = true;
                }
                if(!u_c && upper_case.contains(tmp)){
                    count++;
                    u_c = true;
                }
                if(!no && numbers.contains(tmp)){
                    count++;
                    no = true;
                }
                if(!sp && special_characters.contains(tmp)){
                    count++;
                    sp = true;
                }               
            }
        }
        
        int newX = 4-count+n;
        if(newX > 6){
            return 4-count;
        }else{
            //return 2-n+count+1;
            return 4-count+6-newX;
        }
            
    }
    
   
    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();
    }
}