What brand of coffee does McDonald's use?

I'm curious to know, what specific brand of coffee does McDonald's utilize in their coffee offerings? Is it a proprietary blend that they've developed exclusively for their restaurants, or do they source it from a well-known coffee brand? And if it's the latter, which brand is it? I'm always interested in the details behind the products I consume, and I'm sure many others share this sentiment when it comes to the coffee they enjoy at McDonald's.