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
        boolean num=false;
        boolean special=false;
        boolean upper=false;
        boolean lower=false;
        int count=0;
        int req=0;
        for(int i=0;i<password.length();i++){
            count++;
            int temp=password.charAt(i);
            if(temp>=65&&temp<=90){
                upper=true;
            }
            else if(temp>=97&&temp<=122){
                lower=true;
            }
            else if(temp>=48&&temp<=57){
                num=true;
            }
            else 
                special=true; 
        }
        if(!upper){
            req++;
        }
        if(!lower){
            req++;
        }
        if(!num){
            req++;
        }
        if(!special){
            req++;
        }
        if(req==0){
            if(count>=6)
            return 0;
            else 
                return 6-count;
        }
        else {
            if(count+req>=6){
                return req;
            }
            else
                return (6-count);
        }
    }

    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();
    }
}