I don’t have a gtin or mpn, what to do?

I get the error on my merchant centre :

Hard goods must have values for two out of the following attributes: gtin, brand, mpn. Please make sure to include this required attribute in your data feed. Learn more

But my goos have neither gtin or mpn. I read that I should be able to set a “false” value but I cannot see how. Please help ??