Quantity discount of one free product in WooCommerce

I have three products that I want to give as a free item. If anyone adds more quantity from an item I want to give only one quantity as free. That means deducting price of one quantity from the subtotal. For example: the price of a product is 4 and the total quantity added is 5. So the total subtotal will be 20. Now, I want to deduct the price of one quantity from the subtotal. So, the final outcome will be subtotal 15, after deducting the price.

I have tried this code.

$free_items_id = [344,345,346];
foreach ( $cart->get_cart() as $cart_item_key => $cart_item ) {
if ( in_array( $cart_item['product_id'], $free_items_id ) ) {
   if ( $cart_item['quantity'] > 1 ) {
    $price_to_be_deducted = $cart_item['data']->get_price();
    $updated_price = ( $cart_item['quantity'] - 1 ) * $price_to_be_deducted;
        $cart_item['data']->set_price( $updated_price );
    break;
    }
   else {
    $cart_item['data']->set_price( 0 );
   }
}
}

But this code multiplies the $updated_price with the total quantity number of the product. Can anyone give any solution.

To discount the price of one product (for specific defined products), when the quantity is up to 2, try the following (you can change the minimum required quantity):

add_action( 'woocommerce_before_calculate_totals', 'action_before_calculate_totals');
function action_before_calculate_totals( $cart ) {
    if ((is_admin() && !defined('DOING_AJAX')))
        return;

    if (did_action('woocommerce_before_calculate_totals') >= 2)
        return;

    $targeted_ids  = [344,345,346]; // Here define the valid products Ids
    $qty_threshold = 2; // Here define the minimum quantity required

    foreach ( $cart->get_cart() as $cart_item ) {
        if ( in_array( $cart_item['product_id'], $targeted_ids ) ) {
            $quantity = $cart_item['quantity'];
            if ( $quantity >= $qty_threshold ) {
                $discounted_price = $cart_item['data']->get_price() / $quantity * ($quantity - 1);
                $cart_item['data']->set_price( $discounted_price );
            }
        }
    }
}

Or (in the same way), you can add a global calculated discount subtotal like:

add_action( 'woocommerce_cart_calculate_fees', 'action_cart_calculate_fees', 30, 1 );
function action_cart_calculate_fees( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    $targeted_ids  = [344,345,346]; // Here define the valid products Ids
    $qty_threshold = 2; // Here define the minimum quantity required
    $discount      = 0; // Initializing

    foreach ( $cart->get_cart() as $cart_item ) {
        if ( in_array( $cart_item['product_id'], $targeted_ids ) ) {
            if ( $cart_item['quantity'] >= $qty_threshold ) {
                $discount += $cart_item['data']->get_price();
            }
        }
    } 
    
    if( $discount > 0 ) {
        $cart->add_fee( __( "Quantity discount", "woocommerce" ), -$discount);
    }
}

Both ways should work.