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[] a = new int[4];
        a[0]=1;
        a[1]=1;
        a[2]=1;
        a[3]=1;
        if(n<=3)
        {
             return 6-n;               
        }
        for(int temp=0;temp<n;temp++)
        {
            char r = password.charAt(temp);
            if(r>='a'&&r<='z')
            {
                a[0]=0;
            }else if(r>='A'&&r<='Z')
            {
                a[1]=0;
            }else if(r>='0'&&r<='9')
            {
                a[2]=0;
            }else 
            {
                a[3]=0;
            }
        }
        int ans=0;
        for(int temp=0;temp<4;temp++)
        {
            ans+=a[temp];
        }
        if(n+ans<6)
        {
            return 6-n;
        }
        return ans;
    }
    /*public static boolean check(char r)
    {
        String symbol="!@#$%^&*()-+";
        for(int temp=0;temp<symbol.length();temp++)
        {
            if(r==symbol.charAt(temp))
            {
                return true;
            }
        }
        return false;
    }*/
    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();
    }
}