import UIKit
@UIApplicationMain
class AppDelegate : UIResponder, UIApplicationDelegate {
    var window : UIWindow?
    func application(_ application: UIApplication,
        didFinishLaunchingWithOptions
        launchOptions: [UIApplication.LaunchOptionsKey : Any]?)
        -> Bool {
            self.window = self.window ?? UIWindow()
            self.window!.backgroundColor = .white
            self.window!.rootViewController = ViewController()
            self.window!.makeKeyAndVisible()
            return true
    }
}
