ЕГЭ № 5. Задание 3

from collections import Counter


with open("input.txt", "r", encoding="utf-8") as file:
	buys_count = Counter()
	buys = [line.strip() for line in file.readlines()]

	for buy in buys:
		buys_count.update(buy.split(","))

	max_count = buys_count.most_common(1)[0][1]
	max_buy = ""

	for buy in buys_count.most_common():
		if buy[1] == max_count:
			if buy[0] <= max_buy or max_buy == "":
				max_buy = buy[0]

	print(max_buy)