     }
 
     @IBAction func btnGoPressed(sender: AnyObject) {
+        guard progressBarsLeftArray.contains(-1) else { return }
+
         dispatch_group_async(myGroup, myQueue) {
             //Task 1
             self.animateProgressRun(progressIndex: self.randomProgressBarIndex, withInterval: 0.02)

    func animateProgressRun(progressIndex progressIndex: Int, withInterval interval: NSTimeInterval) {
        for progress in 1...100 {
            NSThread.sleepForTimeInterval(interval)
//                dispatch_group_notify(myGroup, myQueue, {})
            if progress == 50 {
                dispatch_group_wait(myGroup, 2)
            }


    func resetProgressBars() {
        progressBarsLeftArray.removeAll()

        for progressBar in progressBars {
            progressBarsLeftArray.append(-1)
