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 ans=0;
        int b1=0,b2=0,b3=0,b4=0;
        for(int i=0;i<n;i++)
        {
            char x=password.charAt(i);
            if(x>=65 && x<=90)
            {
                b1=1;
            }
            else if(x>=97 && x<=122)
            {
                b2=1;
            }
            else if(x>=48 && x<=57)
            {
                b3=1;
            }
            else
            {
                b4=1;
            }
        }
        if(b1==0)
        {
            ans++;
        }
        if(b2==0)
        {
            ans++;
        }
        if(b3==0)
        {
            ans++;
        }
        if(b4==0)
        {
            ans++;
        }
        if((n+ans)<6)
        {
            ans+=6-n-ans;
        }
        //int p=(int)'9';
        return ans;
    }

    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();
    }
}