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

public class Solution {

    static int minimumNumber(int n, String password) {
        boolean needsLower = true;
        boolean needsUpper = true;
        boolean needsDigit = true;
        boolean needsSpecial = true;
        int i = 0;
        
        while ((needsLower || needsUpper || needsDigit || needsSpecial) && i < n) {
            char ch = password.charAt(i++);
            if (ch >= 'a' && ch <= 'z') needsLower = false;
            else if (ch >= 'A' && ch <= 'Z') needsUpper = false;
            else if (ch >= '0' && ch <= '9') needsDigit = false;
            else needsSpecial = false;
        }
        
        int neededChars = 0;
        if (needsLower) neededChars++;
        if (needsUpper) neededChars++;
        if (needsDigit) neededChars++;
        if (needsSpecial) neededChars++;
        
        if (n < 6 && 6-n > neededChars) return 6-n;
        else return neededChars;
    }

    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();
    }
}