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) {
        // Return the minimum number of characters to make the password strong
        int res=0;
        if(n<6)
            res=6-n;
        int prUpper=0,prLower=0,prDigit=0,prCharacter=0;
        String spclCharacter="!@#$%^&*()-+";
        for(int i=0;i<n;i++)
        {
            char c=password.charAt(i);
            if(Character.isUpperCase(c))
                prUpper++;
            if(Character.isLowerCase(c))
                prLower++;
            if(Character.isDigit(c))
                prDigit++;
            if(spclCharacter.indexOf(c)>=0)
                prCharacter++;
        }
        if(res<4)
        {
            int temp=0;
            if(prUpper>0)
                temp++;
            if(prLower>0)
                temp++;
            if(prDigit>0)
                temp++;
            if(prCharacter>0)
                temp++;
            res=(4-temp)>res?(4-temp):res;
        }
        return res;
    }

    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();
    }
}