<?php

$lines = array_map('str_split', explode("\n", file_get_contents('input.txt')));

$oxygen_lines = $lines;
for ($i = 0, $l = count($oxygen_lines[0]); $i < $l; $i++) {
    if (count($oxygen_lines) <= 1) {
        break;
    }
    $rotated_lines = array_map('array_reverse', array_map(null, ...$oxygen_lines)); // matrix rotation
    $max = determine_max_number_at_line($rotated_lines, $i);
    $oxygen_lines = array_filter($oxygen_lines, static function ($line) use ($max, $i) {
        return $line[$i] == $max;
    });
}

$co2_lines = $lines;
for ($i = 0, $l = count($co2_lines[0]); $i < $l; $i++) {
    if (count($co2_lines) <= 1) {
        break;
    }
    $rotated_lines = array_map('array_reverse', array_map(null, ...$co2_lines)); // matrix rotation
    $min = determine_min_number_at_line($rotated_lines, $i);
    $co2_lines = array_filter($co2_lines, static function ($line) use ($min, $i) {
        return $line[$i] == $min;
    });
}

$oxygen = implode(current($oxygen_lines));
$co2 = implode(current($co2_lines));

echo bindec($oxygen) * bindec($co2);

function determine_max_number_at_line($rotated_lines, $line_number): bool|int|string
{
    $line = $rotated_lines[$line_number];
    $counts = array_count_values($line);
    if ($counts[0] === $counts[1]) {
        return 1;
    }
    return array_search(max($counts), $counts);
}

function determine_min_number_at_line($rotated_lines, $line_number): bool|int|string
{
    $line = $rotated_lines[$line_number];
    $counts = array_count_values($line);
    if ($counts[0] === $counts[1]) {
        return 0;
    }
    return array_search(min($counts), $counts);
}