[radix]

Two men are in a department when they see a deal on socks. The store only carries one brand of socks, but pairs are available in ten different colors (red, blue, green, yellow, black, blown, tan, white, grey, and orange). The store has a sale that specifies that if you buy one pair of each color, you get each pair half off. The two men each decide this is a good deal, and pull one pair of each color off of the metal bars on which the plastic hooks that keep the socks paired together are hung and procede to the checkout counter. Both men wear the same size socks, and it's fortunate they came when they did, because they completely depleted the stores inventory. Anyhow, the clerk rings them up, one man first, then the other. The clerk places ten pairs of socks, each of a different color, in a shopping bag for each man with each pair of socks still clipped together, along with a receipt in each mans respective shopping bag in turn. After the clerk rings them up, and as the men are leaving, the lights in the store go out. The two men crash into each other and the twenty pairs of socks they both purchased spill into one big pile on the floor. Despite the fact that it is pitch black, and nobody had any source of light whatsoever, each man walked out of the store with ten different colored pairs of socks (red, blue, green, yellow, black, blown, tan, white, grey, and orange), in other words, exactly what they purchased. How did they do it?