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) {

        int u=0;
        int l=0;
        int d=0;
        int s =0;
        int t=0;
        int r = 0;
        char arr[] = password.toCharArray();
        for(int i=0;i<n;i++){
            if(Character.isUpperCase(arr[i])){
                u =1;
            }
            if(Character.isLowerCase(arr[i])){
                l =1;
            }
            if(Character.isDigit(arr[i])){
                d =1;
            }
            Pattern p = Pattern.compile("[^A-Za-z0-9]");
            Matcher m = p.matcher(password);
            // boolean b = m.matches();
            boolean b = m.find();
            if(b== true){
                s=1;
            }
        }
        t = u+l+d+s;
        r = 4-t;
        if(n+r >= 6){
          return r;  
        }else
            return(6-t -(n-t) );
        
        
        // Return the minimum number of characters to make the password strong
    }

    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();
    }
}