In ancient Greek mythology, Sisyphus, king of Corinth, was punished for pushing a boulder up a mountain, but no matter how hard he tried, the boulder inevitably rolled down before reaching the top of the mountain, so he had to push it again, endlessly. The famous String of Sisyphus is named after this story.

What is a Sisyphus string? That is to say, take any number, such as 35962, and count the even number, odd number and all numbers in this number, and you can get 2(2 even numbers), 3(3 odd numbers) and 5 (five digits in total), and use these three numbers to form the next number string 235. Repeat the above process for 235 to get 1, 2, 3. Repeating the sequence of 123 will still get 123. 123 is a digital black hole for this "universe" composed of programs and numbers.

Can each number finally get 123? Try with a large number. For example: 88883377499222, in this number, the number of even numbers, odd numbers and all numbers are 1 1, 9 and 20 respectively. Add these three numbers to get 1 1920, which is 1 1920.

This is the mathematical black hole "Sisyphus string".