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

public class strongpassword {

	static int minimumNumber(int n, String password) {
		// Return the minimum number of characters to make the password strong
		StringBuffer sb = new StringBuffer();
		sb.append(password);
		int count = 0;
		boolean num = false, lc = false, uc = false, sc = false;
		int len = n;
		for (int i = 0; i < n; i++) {
			if (sb.charAt(i) >= '0' && sb.charAt(i) <= '9')
				num = true;
			else if (sb.charAt(i) >= 'a' && sb.charAt(i) <= 'z')
				lc = true;
			else if (sb.charAt(i) >= 'A' && sb.charAt(i) <= 'Z')
				uc = true;
			else
				sc = true;
		}
		if (uc == true)
			count++;
		if (lc == true)
			count++;
		if (sc == true)
			count++;
		if (num == true)
			count++;
		if (count < 4) {
			len += (4 - count);
		}
		if (len >= 6)
			return (4 - count);
		else
			return 10 - len - count;

	}

	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();
	}
}