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 u = 0,l=0,num=0,sp=0;
        char a[] = password.toCharArray();
        for(int i=0;i<n;i++)
        {
            if(a[i]>='a' && a[i] <='z')
                l++;
            else if(a[i]>='A' && a[i] <='Z')
                u++;
            else if(a[i]>='0' && a[i] <='9')
                num++;
            else
                sp++;
        }
        
        if(n>=6 && sp>=1&&num>=1&&l>=1&&u>=1)
            return 0;
        int c=0;
        //if(n >= 6)
        //{
            if(sp<1)
                c++;
            if(num<1)
                c++;
            if(l<1)
                c++;
            if(u<1)
                c++;
            
            if(n+c < 6)
                return 6-n;
            return c;
        //}
        
        //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();
    }
}