#!/bin/python

import sys

numbers = "0123456789"
lower_case = "abcdefghijklmnopqrstuvwxyz"
upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
special_characters = "!@#$%^&*()-+"

def minimumNumber(n, password):
    num, low, up, sp = [], [], [], []
    k=0
    for i in password:
        if i in numbers and not num:
            num.append(i)
            k+=1
        elif i in lower_case and not low:
            low.append(i)
            k+=1
        elif i in upper_case and not up:
            up.append(i)
            k+=1
        elif i in special_characters and not sp:
            sp.append(i)
            k+=1
    if n>=6:
        return 4-k
    else:
        if 6-n >4-k:
            return 6-n
        else:
            return 4-k
    
if __name__ == "__main__":
    n = int(raw_input().strip())
    password = raw_input().strip()
    answer = minimumNumber(n, password)
    print answer