Kaprekar Socks

Description: The number 6174 is called "Kaprekar's constant" and is famous for always resulting from the following algorithm: ①: Take any number of four digits (including leading zeroes) which contains at least two different digits. ②: Arrange the digits in descending and in ascending order, yielding two different four-digit numbers. ③: Subtract the smaller of these numbers from the bigger one. ④: Go to step 2 and repeat until convergence. This process will always converge to the number 6174. Don't believe it? Try it out yourself. It's like magic. Wear this distressed design if you are a mathematician or love mathematics and numbers or buy it as a present for the math nerds or mathematicians in your live because all ways lead to 6174.