Crashing app when i want to go rootview from other view controller

I want to go Root view Controller from another view controller but i got the terminating error. following is the error message in console,

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFArray removeObjectsInRange:]: index (4) beyond bounds (1)'
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This is my code for that

NSArray *arr=self.navigationController.viewControllers;
 [self.navigationController popToViewController:[arr objectAtIndex:2] animated:YES];

So any one can give me the suggestion on it so can remove the crash

The NavigationController has a method called to pop to its root view controller. Maybe you should use this one instead.

- (NSArray *)popToRootViewControllerAnimated:(BOOL)animated