/*
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 * and open the template in the editor.
 */

/**
 *
 * @author Nehal Kalnad
 */
import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    static boolean cont(String s , char c)
    {
        for(int i = 0 ; i < s.length() ; i++)
        {
            if(s.charAt(i) == c)
                return true;
        }
        return false;
    }
    static int minimumNumber(int n, String p)
    {
        int uC = 0 , lC = 0, num = 0, spec = 0;
        String numbers = "0123456789";
        String low = "abcdefghijklmnopqrstuvwxyz";
        String up = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        String sp = "!@#$%^&*()-+";
        for(int i = 0 ; i < n ; i++)
        {
            char c = p.charAt(i);
            if(cont(numbers , c))
                num = 1;
            else if(cont(low , c))
                lC = 1;
            else if(cont(up , c))
                uC = 1;
            else if(cont(sp , c))
                spec = 1;                
        }
        int need = 4 - num - lC - uC - spec;
        if(6-n > need)
            return 6-n;
        return need;
    }

    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();
    }
}