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
        int f1=0,f2=0,f3=0,f4=0,count=0;
        for(int i=0;i<n;i++){
            char ch = password.charAt(i);
            if(ch>='0' && ch<='9' && f1 == 0){
                count++;
                f1=1;
            }
            else if(ch>='a' && ch<='z' && f2 == 0){
                count++;
                f2=1;
            }
            else if(ch>='A' && ch<='Z' && f3 == 0){
                count++;
                f3=1;
            }
            else if((ch =='!' || ch =='@' || ch=='#' || ch=='$' || ch=='%' || ch=='^' || ch=='&' || ch=='*' || ch=='(' || ch==')' || ch=='-' || ch=='+')&&(f4==0)){
                count++;
                f4=1;
            }
            
        }
        if(count==4 && n>6){
            return 0;
        }
        else if((4-count)>(6-n)){
            return (4-count);
        }
        else{
            return (6-n);
        }
    }

    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();
    }
}