#!/bin/python

import sys

def minimumNumber(n, password):
    numbers = "0123456789"
    lower_case = "abcdefghijklmnopqrstuvwxyz"
    upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    special_characters = "!@#$%^&*()-+"    
    res=0
    for l in numbers:
        if l in password:
            res+=1
            break
    for l in lower_case:
        if l in password:
            res+=1
            break
    for l in upper_case:
        if l in password:
            res+=1
            break
    for l in special_characters:
        if l in password:
            res+=1
            break
    if len(password)>=6:
        return 4-res
    else:
        return max(4-res,6-len(password))
            
if __name__ == "__main__":
    n = int(raw_input().strip())
    password = raw_input().strip()
    answer = minimumNumber(n, password)
    print answer