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

public class Solution {

    static int minimumNumber(int n, String password) {
        // Return the minimum number of characters to make the password strong
        int l=0,k=0;
        if (password.length() < 6) {
			l = 6 - password.length();

		}
		if (!Pattern.compile("[0-9]+").matcher(password).find()) {
			k++;
		}
		if (!Pattern.compile("[a-z]+").matcher(password).find()) {
			k++;
		}
		if (!Pattern.compile("[A-Z]+").matcher(password).find()) {
			k++;
		}
		if (!Pattern.compile("[^A-Za-z0-9]").matcher(password).find()) {
			k++;
		}
		if (k <= l)
			return l;
		else if (k > l)
			return k;
		else
			return 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();
    }
}