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 hasUpper=false,hasLower=false,hasDigit=false,hasSpecial=false;
        String sp = "!@#$%^&*()-+";
        int cnt=0;
        for(int i=0;i<n;i++){
            char ch = password.charAt(i);
            if(ch>='0' && ch<='9'){
                if(!hasDigit){
                    cnt++;
                }
                hasDigit = true;
            } else if(ch>='a' && ch<='z'){
                if(!hasLower){
                    cnt++;
                }
                hasLower = true;
            } else if(ch>='A' && ch<='Z'){
                if(!hasUpper){
                    cnt++;
                }
                hasUpper = true;
            } else if(sp.indexOf(ch)!= -1){
                if(!hasSpecial){
                    cnt++;
                }
                hasSpecial = true;
            }
        }
        if(cnt>=4 && n>=6 ){
            return 0;
        } else if(n>=6){
            return 4-cnt;
        } else if(n<6) {
            return Math.max(4-cnt,6-n);
        }
        return 0;
    }

    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();
    }
}