Question about OSI Open Source License requirement and new license approval timeline

I’m very interested in participating and noticed the requirement for the project to use an OSI-approved open source license.

Since OSI license approval for a new license typically takes several weeks to months, I wanted to clarify:

Are we allowed to use an existing OSI-approved license (like MIT, Apache 2.0, GPLv3) for our project, or

Is it mandatory to create and get approval for a new OSI license within the hackathon timeline?

Given the tight deadline (39 days), creating a new license and getting it officially approved by OSI within this timeframe is very unlikely.

Could you please advise on how you recommend we meet this license requirement?

Thanks for your guidance!