How to benefit from update discount offered by Oreilly in case of 2nd edition of The Definitive Antlr 4 Reference, 2nd ed?

Hello OReilly Team

I bought the 1st ed of The Definitive ANTLR Reference, print version (there was no option to buy ebooks back then).
I know Orreily have an offer (discount) for updated version, but regarding ebooks only.
I would like to benefit from this discount when I will buy the 2nd edition of the book in ebook format.
Could you please advice me how can I do that if possible?

Thank you in advance.
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