#!/bin/python3

import sys

def minimumNumber(n, password):
    # Return the minimum number of characters to make the password strong
    a= list("0123456789")
    b= list("abcdefghijklmnopqrstuvwxyz")
    c= list("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
    d=list("!@#$%^&*()-+")
    c1=c2=c3=c4=0
    for i in range(n):
        if(password[i] in a):
            c1=1
        elif(password[i] in b):
            c2=1
        elif(password[i] in c):
            c3=1
        else:
            c4=1
    return max(4-c1-c2-c3-c4,6-n)
        

if __name__ == "__main__":
    n = int(input().strip())
    password = input().strip()
    answer = minimumNumber(n, password)
    print(answer)