<?php

$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
$coordinates = [];
$folds = [];
foreach ($input as $line) {
    if (strstr($line, 'fold')) {
        preg_match('#fold along ([x|y])=(\d*)#', $line, $found);
        $folds[] = [$found[1], (int)$found[2]];
    } else {
        $point = explode(',', $line);
        $coordinates[] = $point;
    }
}
foreach ($folds as $fold) {
    foreach ($coordinates as &$point) {
        if ($fold[0] == 'x') {
            if ($point[0] > $fold[1]) {
                $point[0] = $fold[1] * 2 - $point[0];
            }
        }
        if ($fold[0] == 'y') {
            if ($point[1] > $fold[1]) {
                $point[1] = $fold[1] * 2 - $point[1];
            }
        }
    }
    $coordinates = points_unique($coordinates);
    echo count($coordinates); //751
    die();
}

function points_unique($coordinates)
{
    $tmp = [];
    $newCoordinates = [];
    foreach ($coordinates as $point) {
        if (!isset($tmp[implode(',', $point)])) {
            $newCoordinates[] = $point;
            $tmp[implode(',', $point)] = 1;
        }
    }
    return $newCoordinates;
}