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

public class Solution {
    static boolean checkDigits(char c) {
        if(c >= '0' && c <= '9')
            return true;
        return false;
    }
    static boolean checkLower(char c) {
        if(c >= 'a' && c <= 'z')
            return true;
        return false;
    }
    static boolean checkUpper(char c) {
        if(c >= 'A' && c <= 'Z')
            return true;
        return false;
    }
    static int minimumNumber(int n, String password) {
        boolean lowerCase = false;
        boolean upperCase = false;
        boolean digits = false;
        boolean special = false;
        for(int i = 0; i < n; i++) {
            if(lowerCase && upperCase && digits && special){
                if(n >= 6)
                    return 0;
                else return(6 - n);
            }
            char c = password.charAt(i);
            if(checkDigits(c))
                digits = true;
            else if(checkLower(c))
                lowerCase = true;
            else if(checkUpper(c))
                upperCase = true;
            else
                special = true;
        }
        int count = 0;
        if(!lowerCase)
            count++;
        if(!upperCase)
            count++;
        if(!digits)
            count++;
        if(!special)
            count++;
        if((n+count) >= 6)
            return count;
        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();
    }
}