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=0,b=0,c1=0,d=0,sum=0,result=0;
        for(int i=0;i<n;i++)
        {
          char c=password.charAt(i);
            if(c>='a'&&c<='z') a=1;
            if(c>='A'&&c<='Z') b=1;
            if(c>='0'&&c<='9') c1=1;
            if(((int)c>=32&&(int)c<=47)||((int)c>=58&&(int)c<=64)) d=1;
            
        }
         sum=a+b+c1+d;
         result=4-sum;
        if(n<6)
            result=Math.max(result,6-n);
        return result;
        
        // Return the minimum number of characters to make the password strong
    }

    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();
    }
}