using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static int minimumNumber(int n, string password) {
        // Return the minimum number of characters to make the password strong
        //const string numbers = "0123456789";
        //const string lower_case = "abcdefghijklmnopqrstuvwxyz";
        //const string upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        const string special_characters = "!@#$%^&*()-+";
        
        var isDigit = false;
        var isLower = false;
        var isUpper = false;
        var isSpecial = false;
        var rulesCount = 0;
        
        foreach(char c in password){
            if(char.IsDigit(c)){
                if(!isDigit){
                    isDigit = true;
                    rulesCount++;
                }
            }
            else if(char.IsLower(c)){
                if(!isLower){
                    isLower = true;
                    rulesCount++;
                }
            }
            else if(char.IsUpper(c)){
                if(!isUpper){
                    isUpper = true;
                    rulesCount++;
                }
            }
            else if(special_characters.Contains(c)){
                if(!isSpecial){
                    isSpecial = true;
                    rulesCount++;
                }
            }else{
                //invalid password
                return -1;
            }
            
        }
        
        if(rulesCount == 4 && password.Length >= 6)
            return 0;
        
        var diffp = (6-password.Length);
        var diffrc = (4-rulesCount);
        
        return Math.Max(diffp, diffrc);
    }

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        string password = Console.ReadLine();
        int answer = minimumNumber(n, password);
        Console.WriteLine(answer);
    }
}