import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		String word = scan.next();
		ArrayList<String> list = new ArrayList<>();
		list.add("0123456789");
		list.add("abcdefghijklmnopqrstuvwxyz");
		list.add("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
		list.add("!@#$%^&*()-+");
		for (int i = 0; i < n; i++) {
			char ch = word.charAt(i);
			for (int j = 0; j < list.size(); j++) {
				if (list.get(j).contains("" + ch)) {
					list.remove(j);
					break;
				}
			}
		}
		System.out.println(Math.max(list.size(), 6 - n));
		scan.close();
    }
}