Add 1 item to cart as Woocommerce different items?

Question

WordPress

Hello everyone, I have implemented an additional input for entering the length in the product card. The price of the goods is indicated per meter, a person enters, enters the length of the pole, the number of pieces, and the total number of meters and the amount are calculated for him. When I click on the add to cart button, I change the price of the product as follows:

add_action( 'woocommerce_before_calculate_totals', 'add_custom_price' );
function add_custom_price( $cart_object ) {
    $length = (int)$_POST['length'];
    $price = (int)$_POST['price'];
    $itog = ($length / 1000)*$price;
    $target_product_id = 15713;
    foreach ( $cart_object->cart_contents as $key => $value ) {
        if ( $value['product_id'] == $target_product_id ) {
            $value['data']->set_price((int)$itog);
        }
    }
}

Thus, the desired price of the product is added, but if the user wants to add the same columns of a different size, the goods in the basket are added and the price is overwritten already from the new length of the column. The question is, how can I add 1 and the same product to the cart in different positions? Plugins are a huge request not to offer, I know that there is something similar but it does not suit me.