#!/usr/bin/python3
from pprint import pprint
import re

rules = {}
with open("input") as fh:
    for ln in fh:
        m = re.fullmatch(r"(.*) bags contain (.*)\.\n", ln)
        container = m.group(1)
        contents = {}
        for c in m.group(2).split(", "):
            if m := re.match(r"(\d+) (.*) bag", c):
                contents[m.group(2)] = int(m.group(1))
        assert container not in rules # Assume only one rule for each container
        rules[container] = contents

containers = { "shiny gold" }
while True:
    new_containers = set()
    for c in containers:
        for r in rules.items():
            if c in r[1]:
                new_containers.add(r[0])
    combined_containers = containers | new_containers
    pprint(combined_containers)
    if combined_containers == containers:
        # nothing added, so we are finished
        break
    containers = combined_containers
print(len(combined_containers - { "shiny gold" }))