[mikeash]

Very nice. It took me a while to see why that works, so I wonder how long it would have taken me to come up with it.

Now that I get it, it seems almost obvious. It's basically the same as my solution, except I'm essentially using this technique on 50 separate lines of 2 people each.

[ssfermoy]

Glad you like it. Heard this as an interview question at a trading company. Gave something similar to your solution and was asked for a better one, eventually work my way to the solution above but was given no indication if it was what they wanted. It wasn't a pleasant experience.