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) {
        // Return the minimum number of characters to make the password strong
        int a=0,a0=0;
        int a1=0,a2=0,a3=0,a4=0;
        
        for(int i=0;i<n;i++)
        {
            char ch=password.charAt(i);
            if(ch=='a' || ch=='b' || ch=='c' || ch=='d' || ch=='e' || ch=='f' || ch=='g' || ch=='h' || ch=='i' || ch=='j' || ch=='k' || ch=='l' || ch=='m' || ch=='n' || ch=='o' || ch=='p' || ch=='q' || ch=='r' || ch=='s' || ch=='t' || ch=='u' || ch=='v' || ch=='w' || ch=='x' || ch=='y' || ch=='z'  )
            {
                a1++;
            }
                if(ch=='A' || ch=='B' || ch=='C' || ch=='D' || ch=='E' || ch=='F' || ch=='G' || ch=='H' || ch=='I' || ch=='J' || ch=='K' || ch=='L' || ch=='M' || ch=='N' || ch=='O' || ch=='P' || ch=='Q' || ch=='R' || ch=='S' || ch=='T' || ch=='U' || ch=='V' || ch=='W' || ch=='X' || ch=='Y' || ch=='Z'  )
            {
                a2++;
            }
            if(ch=='1' || ch=='2' || ch=='3' || ch=='4' || ch=='5' || ch=='6' || ch=='7' || ch=='8' || ch=='9' || ch=='0' )
            {
                a3++;
            }
            if(ch=='!' ||ch=='@' ||ch=='#' ||ch=='$' ||ch=='%' ||ch=='^' ||ch=='&' ||ch=='*' ||ch=='(' ||ch==')' ||ch=='-' ||ch=='+')
            {
                a4++;
            }
        }
         if(a1==0)
            {
               a0++;
               }         
               if(a2==0)
            {
               a0++;
               }  
             if(a3==0)
            {
               a0++;
               }
                if(a4==0)
            {
               a0++;
               }   
        
            a=(6-n);
            if(a>a0)
            {
                a0=a;
            }
              
        return(a0);
                    
    }

    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();
    }
}