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 required=0;
        int[] found=new int[5];
        
        int k=0;
       
        
        
        for(int i=0;i<n;i++){
            char c=password.charAt(i);
            if(found[1]==0 && c>=48 && c<58)
            {found[1]=1;
                k++;}
            else if(found[2]==0 && c>=97 && c<=122)
            {found[2]=1;
                k++;}
            else if(found[3]==0 && c>=65 && c<=90)
            {found[3]=1;
                k++;}
            else if(found[4]==0)
            { String special_characters = "!@#$%^&*()-+";
             for(int l=0;l<special_characters.length();l++)
                if(c==special_characters.charAt(l))
                {found[4]=1;
                k++;
                 break;}
            }
           
            
        }
         return Math.max(4-k,6-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();
    }
}