import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    

    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();
    }
    public static int minimumNumber(int n,String st)
    {
        String numbers = "0123456789";
        String lower_case = "abcdefghijklmnopqrstuvwxyz";
        String upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        String special_characters = "!@#$%^&*()-+";
        int a[]=new int[4];
        int i=0;
        char ch;
        for(i=0 ;i<4;i++)
        {a[i]=0;}
        for(i=0;i<n;i++)
        {
            ch=st.charAt(i);
            if(lower_case.indexOf(ch)!=-1 && a[0]==0)
            {a[0]=1;}
            if(upper_case.indexOf(ch)!=-1 && a[1]==0)
            {a[1]=1;}
            if(numbers.indexOf(ch)!=-1 && a[2]==0)
            {a[2]=1;}
            if(special_characters.indexOf(ch)!=-1 && a[3]==0)
            {a[3]=1;}
        }
        int c=0;
        for(i=0;i<4;i++)
        {
            if(a[i]==0)
            {c++;}
        }
        if(st.length()>=6)
        {
            return c;
        }
        if(6-st.length()<c)
        {
            return c;
        }else
        {
            return 6-st.length();
        }
        
    }
}