<?php

$lines = array_filter(explode("\n", file_get_contents('./input.txt')), fn($line) => !empty($line));

echo array_sum(array_map(
    static function($line) {
        $numbers = array_values(array_filter(array_map(static fn($letter) => is_numeric($letter) ? $letter : null, str_split($line))));

        return (int) sprintf('%s%s', $numbers[0], array_pop($numbers));
    },
    $lines
));