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";
        String lower_case = "abcdefghijklmnopqrstuvwxyz";
        String upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        String special_characters = "!@#$%^&*()-+";
        int num,sp,lw,up;
        num=sp=lw=up=0;
        for (int i=0;i<n;i++)
        {
            if (numbers.indexOf(password.charAt(i))>=0)
                num++;
            else if (special_characters.indexOf(password.charAt(i))>=0)
                sp++;
            else if (lower_case.indexOf(password.charAt(i))>=0)
                lw++;
            else if (upper_case.indexOf(password.charAt(i))>=0)
                up++;
        }
        if (num>0&&sp>0&&lw>0&&up>0&&n>=6)
            return 0;
        else if (num>0&&sp>0&&lw>0&&up>0)
            return (6-n);
        else
        {
            int k=0;
            if (num==0)
                k++;
            if (sp==0)
                k++;
            if (lw==0)
                k++;
            if (up==0)
                k++;
            if (n+k>=6)
                return k;
            else
                return (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();
    }
}