Route $z$ connects cities 5 and 6: in total there are $(n-3)(n-4)/2$ routes connecting cities $j$ and $\ell$, where $j, \ell \geq 4$.
Clare (like gare) is a Chalkdust editor. In her spare time, she’s an assistant professor at Durham University. She likes Skittles, probability, and making the magazine look more like Cosmo.
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