using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static int minimumNumber(int n, string password) {
        int count = password.Length;
        int charCount = 0;
    int[] arr = new int[4];
    int result = 0;
    
    foreach(char c in password)
    {
        if(c >= 48 && c <= 57)
            arr[0] = 1;
        
        if(c >= 65 && c <= 90)
            arr[1] = 1;
        
        if(c >= 97 && c <= 122)
            arr[2] = 1;
        
        if(c >= 33 && c <= 47)
            arr[3] = 1;
    }
    
    int i = 3;
        
    while(i >=0)
    {
        //Console.WriteLine(arr[i]);
        
        if(arr[i] == 1)
            charCount++;
        
        i--;
    }
        
    if(charCount < 4)
        result = 4 - charCount;
    
    if(count + result < 6)
    {
        result = 6 - count;
    }
    
    return result;
    }

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        string password = Console.ReadLine();
        int answer = minimumNumber(n, password);
        Console.WriteLine(answer);
    }
}