How to transfer BBM contacts?

So I have a blackberry, and a iPhone 4s, I want to transfer my contacts to my iPhone 4s. Does anyone know how to?

If I install BBM on my iPhone, it would ask for my Blackberry ID? Am I supposed to log in my blackberry ID and then all my contacts will be there, if not, do you know how?

Best luck.
http://www.macworld.co.uk/how-to/iphone/how-transfer-contacts-blackberry-iphone-3465033/

Yes That's What I did

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