import sys
import typing


def main() -> int:
    counts_sum = sum([c for c in _iter_group_counts(sys.stdin)])
    print(f"counts_sum={counts_sum}")

    return 0


def _iter_group_counts(instream: typing.TextIO) -> typing.Generator[int, None, None]:
    for i, group in enumerate(_iter_groups(instream)):
        answers = set(list(group[0]))
        print(f"i={i} initial={answers}")

        for answers_text in group[1:]:
            to_add = set(list(answers_text))
            answers = answers.intersection(set(list(answers_text)))
            print(f"i={i} added={to_add} result={answers}")

        print(f"i={i} final={answers} n={len(answers)}")
        yield len(answers)


def _iter_groups(instream):
    cur_group = []

    for line in instream:
        line = line.strip()
        if line == "":
            yield cur_group
            cur_group = []
            continue

        cur_group.append(line)

    yield cur_group


if __name__ == "__main__":
    sys.exit(main())