lol = set()
kek = set()

def read_companies(file):
    with open(file) as f:
        data = f.read()
    return data.strip().split()

files = ["ilon.txt", "bill.txt", "sasha.txt"]

for file in files:
    for company in read_companies(file):
        if company not in lol:
            lol.append(company)
        elif company not in kek:
            kek.append(company)

print(len(kek))