What's the pixel dimensions of a presentation slide for Open Office / Libre Office Impress?

What's the dimensions of a presentation slide in pixels?

I'm having a hard time trying to get it right. I keep guessing and checking and it's taking too long. I googled some results and they're a bit off as well.

The other issue is that I'm using .opd format; the format proprietary to open office / libre office in windows 7.

I'm just trying to design a decent background for my presentation.