RU-ALLRUSSIAN 1991 Problem 17
A sequence of positive integers is constructed as follows. If the last digit of is greater than 5, then is . If the last digit of is 5 or less and has more than one digit, then is obtained from by deleting the last digit. If has only one digit, which is 5 or less, then the sequence terminates. Can we choose the first member of the sequence so that it does not terminate?
Dataset text NuminaMath olympiads. Quoted with source.
Solutions
No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.