Set an arbitrary number string and count even numbers, odd numbers and the total number of all digits contained in this number.

For example: 1234567890,

Even number: Count the even numbers in this number, in this example, 2, 4, 6, 8, 0, and there are five in total.

Odd number: Count the odd numbers in this number. In this case, it is 1, 3, 5, 7, 9, a total of five.

Total: Count the total number, in this case, 10.

New number: arrange the answers in the order of "parity total" to get a new number: 55 10.

Repeat: Repeat the operation of the new number 55 10 according to the above algorithm to get the new number: 134.

Repeat: Repeat the operation of the new number 134 according to the above algorithm to get the new number: 123.

Conclusion: Logarithm 1234567890, according to the above algorithm, the final result will be 123. We can write a program with a computer, and test that any number will be 123 after a limited number of repetitions. In other words, the final result of any number cannot escape from the 123 black hole.