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
//        numbers = "0123456789";
//        lower_case = "abcdefghijklmnopqrstuvwxyz";
//        upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
//        special_characters = "!@#$%^&*()-+";//33 100 35 36 37 38 94 40 41 45 43
        int ret = 4;
        boolean containDig= false, containUp=false, containLow=false, containSp=false; 
        for(int i =0 ; i < n; i++){
            if(!containDig && password.charAt(i) >47 && password.charAt(i)<58){
                //is digit
                containDig = true;
                ret--;
            }else if(!containUp && password.charAt(i) >64 && password.charAt(i)<91){
                //us upper
                containUp = true;
                ret--;
                
            }else if(!containLow && password.charAt(i) >96 && password.charAt(i)<123){
                //is lower
                containLow = true;
                ret--;
            }
            else if(!containSp && password.charAt(i) >32 && password.charAt(i)<46){
                if(password.charAt(i) !=34 && password.charAt(i) !=39 && password.charAt(i) !=42 && password.charAt(i) !=44){
                    //is sp
                    containSp = true;
                    ret--;
                }
            }else if(!containSp && password.charAt(i) ==100 && password.charAt(i) ==94){
                //is sp
                containSp = true;
                ret--;
            }
        }
        
        if(n >= 6){
            return ret;
        }else{
            int contain = 4 - ret;
            int dif = 6- n;
            if(dif >= ret){
                return dif;
            }else{
                return ret;
            }
        }
        
    }

    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();
        
        
    }
}