with open("6.txt") as f:
    data = f.read().split("\n\n")
    def process(lines):
        return len(set("".join(lines.split("\n"))))
    print(sum(map(process, data)))

from functools import reduce
with open("6.txt") as f:
    data = f.read().split("\n\n")
    def process(lines):
        lines = lines.strip()
        letters = reduce(set.intersection, map(set, map(list, lines.split("\n"))))
        print(repr(lines), letters)
        return len(letters)
    print(sum(map(process, data)))