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 d=6-password.length();
            int l=0,u=0,s=0,dg=0;
            for(int i=0;i<password.length();i++)
            {
                char ch=password.charAt(i);
                if(ch>=97&&ch<=122)
                    l=1;
                else if(ch>=65&&ch<=90)
                    u=1;
                else if(ch>=48&&ch<=57)
                    dg=1;
                else 
                    s=1;
                
            }
            int req=u+l+dg+s;
            req=4-req;
            //System.out.println(d);
            return Math.max(d,req);
        // Return the minimum number of characters to make the password strong
    }

    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();
    }
}