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) {
        boolean hasLower = false;
        boolean hasUpper = false;
        boolean hasSpecial = false;
        boolean hasDigit = false;
        for(int i=0; i < password.length(); i++) {
            int charValue = (int)(password.charAt(i));
            boolean notSpecial = false;
            if(charValue <= 122 && charValue >= 97) {
                hasLower = true;
                notSpecial = true;
            }
            if(charValue <= 90 && charValue >= 65) {
                hasUpper = true;
                notSpecial = true;
            }
            if(charValue <= 57 && charValue >= 48) {
                hasDigit = true;
                notSpecial = true;
            }
            if(!notSpecial) {
                hasSpecial = true;
            }
        }
        int numOfDigits = 6 - password.length();
             
                int count = 0;
                if(!hasLower) {
                    count++;
                }
                if(!hasUpper) {
                    count++;
                }
                if(!hasSpecial) {
                    count++;
                }
                if(!hasDigit) {
                    count++;
                }
                int res =  numOfDigits > count ? numOfDigits : count;
                return res;
           
    }

    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();
    }
}