CF814D An overnight dance in discotheque

The crowdedness of the discotheque would never stop our friends from having fun, but a bit more spaciousness won't hurt, will it? The discotheque can be seen as an infinite $ xy $ -plane, in which there are a total of $ n $ dancers. Once someone starts moving around, they will move only inside their own movement range, which is a circular area $ C_{i} $ described by a center $ (x_{i},y_{i}) $ and a radius $ r_{i} $ . No two ranges' borders have more than one common point, that is for every pair $ (i,j) $ ( $ 1

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The first sample corresponds to the illustrations in the legend.