iOS touchesBegan issue
===

I have an NSArray whit 15 UIImageViews: 

    @interface ViewController : UIViewController{
        
        NSArray *ArrayImages1;
        NSArray *ArrayImages2;
        
    }

in viewDidLoad: 

     ArrayImages1 = [[NSArray alloc] initWithObjects: a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, nil];
Where a1, a2... are the outlets of the UIImageViews
And the same for ArrayImages2

TouchesBegan and TouchesMoved:

    -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
    {
        UITouch *touch = [touches anyObject];
        CGPoint point = [touch locationInView:self.view];
        UIImageView *posible;
        int imagen;
        if (point.x < 161) {
            imagen = Contador1;
            if (Contador1 > 14) {imagen = Contador1 - 15;}
            imagen--;
            posible = [ArrayImages1 objectAtIndex:imagen];
        }
        else if (point.x > 159) {
            imagen = Contador2;
            if (Contador2 > 14) {imagen = Contador2 - 15;}
            imagen--;
            posible = [ArrayImages2 objectAtIndex:imagen];
        }
        if ([touch view] != posible) { return; }
        original2 = posible.center;    
    }
    
    
    -(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
    {
        UITouch *touch = [touches anyObject];
        CGPoint point = [touch locationInView:self.view];
        UIImageView *posible;
        int imagen;
        if (point.x < 161) {
            imagen = Contador1;
            if (Contador1 > 14) {imagen = Contador1 - 15;}
            imagen--;
            posible = [ArrayImages1 objectAtIndex:imagen];
        }
        else if (point.x > 159) {
            imagen = Contador2;
            if (Contador2 > 14) {imagen = Contador2 - 15;}
            imagen--;
            posible = [ArrayImages2 objectAtIndex:imagen];
        }
        if ([touch view] != posible) { return; }
        posible.center = point;
    }

I have to know if the touch was in one of the two posible UIImageViews, and if it was, move it.
The Contador1 and Contador2 ints, are counters that counts how many UIImageView are visible, the user only can move the last 2 of them.

It works, the thing is when i touch outside, it makes the app crash.
If i change in touchesBegan and TouchesMoved, the index of "posible = [ArrayImage..", for 0, it only works for the first UIImageView (i understand why), but it doesent crash.

Any ideas?