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

public class Solution {

    private static char special[] = "!@#$%^&*()-+".toCharArray();
    
    private static boolean contains(char c) {
        for (int i = 0; i < special.length; i++) {
            if (c == special[i])
                return true;
        }
        return false;
    }
    static int minimumNumber(int n, String password) {
        int u = 0;
        int l = 0;
        int d = 0;
        int s = 0;
        
        for (Character c : password.toCharArray()) {
            if (c >= '0' && c <= '9') {
                d = 1;
            }
            else if (c >= 'a' && c <= 'z') {
                l = 1;
            }
            else if (c >= 'A' && c <= 'Z') {
                u = 1;
            }
            else if (contains(c)) {
                s = 1;
            }
        }
        
        return Math.max(4 - u - l - d - s, 6 - password.length());
    }

    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();
    }
}