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 str) {
        int d=0,l=0,s=0,u=0;
 
    for(int i=0;i < str.length();i++) {
       char ch = str.charAt(i);
        if( Character.isDigit(ch)) {
            d=1;
        }
        else if (Character.isUpperCase(ch)) {
            u=1;
        } else if (Character.isLowerCase(ch)) {
           l=1;
        }
        else
        {
            s=1;
        }
  }
        int ret=0;
        int total=l+u+d+s;
        int t1=0,t2=0;
        
        if(total==4 && n>6)
        {
           
        }
        else if(total<4 || n<6)
        {
            t1=6-n;
            t2=4-total;
            if(t1>t2)ret=t1; else ret=t2;
        }
        
        return ret;
   }

    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();
    }
}