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def middle_page_if_update_correct(update: list[str], rules: list[tuple[str, str]]) -> int:
for idx, page in enumerate(update):
for previous_page in (update[previous_idx] for previous_idx in range(idx)):
if (page, previous_page) in rules:
return 0
return int(update[len(update) // 2])
rules = []
updates = []
reading_updates = False
with open("input") as f:
for line in f.readlines():
if reading_updates:
updates.append(line.strip().split(","))
elif line == "\n":
reading_updates = True
else:
rules.append(tuple(line.strip().split("|")))
result = 0
for update in updates:
result += middle_page_if_update_correct(update, rules)
print(result)
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