Being at the Adidas store in Madrid reminded me of the first time I heard the story of the Dassler brothers, Adi and Rudi. Adi, (get it, ADIDASsler), is the founder of Adidas and Rudi, the founder of Puma. For those of you who don’t know this story, you can read all about it on Fortune’s list of the 50 greatest business rivalries of all time. And in case you were wondering what the #1 greatest business rivalry is, it’s a bit closer to home. Okay, spoiler alert, it’s Coke vs. Pepsi.