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 pwd) {
        // Return the minimum number of characters to make the password strong
            int a=0;int dig=0,low=0,up=0,spec=0;
            for(int i=0;i<n;i++)
            {
                    char ch=pwd.charAt(i);
                    if(ch>64 &&ch<=90)
                    {
                            up++;
                    }
                    else if(ch>=97 && ch<=122)
                            low++;
                    else if(ch>=48&&ch<=57)
                            dig++;
                    else
                            spec++;
                    a++;
                    
            }
            int f=0;
            if(6-a >0)
            {
                    f=6-a;
                    
            }
            int sum=0;
            if(up==0)
                    sum++;
            if(low==0)
                    sum++;
            if(dig==0)
                    sum++;
            if(spec==0)
                    sum++;
            if(f>sum)
                    return f;
            else
                    return sum;
                   
           
    }

    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();
    }
}