<?php

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

foreach ($numbers as $i => $number_1) {
    foreach ($numbers as $j => $number_2) {
        if ($j <= $i) {
            continue;
        }

        if ($number_1 + $number_2 >= 2020) {
            continue;
        }

        $number_to_2020 = 2020 - $number_1 - $number_2;

        if (in_array($number_to_2020, $numbers, true)) {
            echo $number_to_2020 * $number_1 * $number_2;
            exit;
        }
    }
}