report = []

with open("input.txt") as f:
	lines = f.read().split('\n')
	for line in lines:
		report.append(line)

gamma = ''
power = 2 ** len(report[0]) - 1

for i in range(len(report[0])):
    ones_count = 0
    for number in report:
        if number[i] == '1':
            ones_count += 1

    half = len(report) / 2
    if ones_count > half:
        gamma += '1'
    else:
        gamma += '0'

gamma = int(gamma, 2)
epsilon = power - gamma
part1 = gamma * epsilon
print(part1)

o2 = co2 = 0