title: Android back button in device
body: <p>I have Activity A (Main) and Activity B.
  From A, I can go to B. When I test I do the next:</p>
  
  <p>Go from A (a1) to B (b1). Then go back to A (a1). The again from A (a1) to B (b2) and go back to A (a1). </p>
  
  <p>If I push the back button again after doing what I said, I want to exit the app but it returns to the first instance of B (b1), and then if I push again, it goes to the first instance of A(a1) and if a push again now it exit the app.</p>
  
  <p>I don't want this behavior, if I am in activity A and push back button I want to exit the app, not to go to every instance of activities until goes to the first one and then exit.</p>
  
  <p>I hope I was clear.</p>