Text 
A class 

At a quarter to nine, the doors of the auditorium were opened, and students began to enter.
Most of them were dressed casually in jeans and Tshirts. A few wore a suit and a tie.
All of them carried their notebooks and other belongings in a backpack.
They were going to attend their first math class on the theory of measure.
The 300 seat auditorium was slowly filling up.
When François arrived, he had to look for an empty seat.
He climbed to the third row where he saw one still free between two other students.
The noise of the conversations was dominating the room.
François leaned toward his right neighbor:
F.: Hello. My name is François, from France. What's your name?
D.: Hi. I'm Dragomir. I come from Serbia.
F.: I thought I had learned everything I needed to know about measuring things in primary school.
D.: So did I. I had never thought I would need a higher math course on the subject.
At nine o'clock the professor came in.
The auditorium became instantly quiet.
Prof.: Hello everyone. I'm professor Chung. Welcome to my course on measure theory.
Prof.: Before we start, I'm going to hand out these cards. Please fill them out, and turn them in at the end of the class. They will be useful for me to know the students better.
The professor began his course, explaining the basics of set theory, and the concept of measure of a set.
This applied not only to intervals [a, b] on the line of numbers (the measure being ba), or the surface areas on a plane but also to more complicated mathematical objects.
At some point he wrote on the board: "I O U the proof that S is measurable."
François was puzzled. He told Dragomir:
F.: He didn't define these variables I, O and U. Do you know what they are?
François raised his hand and, when invited to speak, asked the teacher.
The whole auditorium burst into laughter.
Prof.: It's an abbreviation to mean "I owe you". I'll give you the proof later. Remind me if I forget.
At the end of the class, François packed his stuff and left his seat. He was making his way to the door when he ran into Jamie, an American friend he had met in Paris the summer before.
F.: Hey Jamie, what are you doing here? I thought you were studying electrical engineering in Europe.
J.: I was last year. But since then I got accepted at Stanford. I joined the Master's program here. And the first year we have to take fundamental courses in maths and physics.
F.: It's great to see you. So how have you been?
J.: Good. It's wonderful to see you too. We will be able to catch up.
F.: Yeah. Unfortunately I've got to go now. Do you sometimes come to the cafeteria?