Altitude sickness or caffeine withdrawal?

I met a lovely person from Australia this afternoon on the bus from Machu Picchu to Aqua Caliente. We both were speculating whether our slight headaches were induced by altitude sickness or caffeine withdrawal.We are both major coffee consumers and it has been hard to keep up our normal consumption in Peru. After two cappuccinos in Aqua Caliente, I’m feeling amazing and thinking was definitely the caffeine withdrawal.