import UIKit

class ViewController: UIViewController {
    var isFirst = true
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    override var preferredFocusEnvironments: [UIFocusEnvironment] {
        if isFirst {
            isFirst = false
            return childViewControllers.last!.preferredFocusEnvironments
        } else {
            return super.preferredFocusEnvironments
        }
    }
}