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
     String   numbers = "0123456789";
     char[] pass = password.toCharArray();
     String lower_case = "abcdefghijklmnopqrstuvwxyz";
     String upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
     String special_characters = "!@#$%^&*()-+";
     int[] arr={0,0,0,0};
     for(int i=0;i<n;i++)
     {
         if(numbers.indexOf(pass[i])!=-1)
             arr[0]=1;
         else if(lower_case.indexOf(pass[i])!=-1)
             arr[1]=1;
         else if(upper_case.indexOf(pass[i])!=-1)
             arr[2]=1;
         else if(special_characters.indexOf(pass[i])!=-1)
             arr[3]=1;
     }
     int sum=arr[0]+arr[1]+arr[2]+arr[3];
     if(n<6)
     {
         int x=6-n;
           int y=4-sum;
        if(x>y)
            return x;
        else
            return y;
     }
     return 4-sum;
    }

    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();
    }
}