The Cuban “line” to buy internet cards: you call out “último?” (“Last?”) to the ambiguous mass of people and then mentally place yourself behind whoever answers. To make doubly sure, you may also ask said person who is in front of them. By the time I figured it out and raised my hand to a call of “último?”, I was politely informed that there were already 2-3 people in line behind me. Glad someone’s mentally keeping track. As to how I managed to get myself in line in the first place, I’m still not exactly sure.