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) 
    {
        int lower=0,upper=0,digit=0,spl=0,total=0;
        // Return the minimum number of characters to make the password strong
        for(int i=0;i<n;i++)
        {
            char c=password.charAt(i);
            if(c>='a' && c<='z')
                lower++;
            else if(c>='A'&& c<='Z')
                upper++;
            else if(c>='0'&& c<='9')
                digit++;
            else
                spl++;
        }
       
           if(lower>0)
               total++;
            if(upper>0)
                total++;
            if(digit>0)
                total++;
            if(spl>0)
                total++;
         if((n+(4-total))>=6)
        {
            return (4-total);
        }
        else
        {
            return (4-total+(6-n-(4-total)));
        }
    }

    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();
    }
}