def part1():
    with open("in.txt") as f:
        # Group's answer can be a set of all characters irrespective of which individual contributed the character
        group_answer_sets = [
            set(c for c in i if c != "\n") for i in f.read().split("\n\n")
        ]
    print(sum(len(answer) for answer in group_answer_sets))


part1()
