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 x) {
        int fl=1,fu=1,fd=1,fs=1,i=0;
        if(n<6){
            for(i=0;i<n;i++){
                if((x.charAt(i)>='a')&&(x.charAt(i)<='z')){
                    fl=0;
                    continue;
                }
                else if((x.charAt(i)>='A')&&(x.charAt(i)<='Z')){
                    fu=0;
                    continue;
                }
                else if((x.charAt(i)>='0')&&(x.charAt(i)<='9')){
                    fd=0;
                    continue;
                }
                else{
                    fs=0;
                    continue;
                }
            }
            int y=(6-n)>(fl+fu+fd+fs)?(6-n):(fl+fu+fd+fs);
            return y;
        }
        else{
            for(i=0;i<n;i++){
                if((x.charAt(i)>='a')&&(x.charAt(i)<='z')){
                    fl=0;
                    continue;
                }
                else if((x.charAt(i)>='A')&&(x.charAt(i)<='Z')){
                    fu=0;
                    continue;
                }
                else if((x.charAt(i)>='0')&&(x.charAt(i)<='9')){
                    fd=0;
                    continue;
                }
                else{
                    fs=0;
                    continue;
                }
            }
            return (fl+fu+fd+fs);
        }
    }

    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();
    }
}