feat(archive/imo): formalize IMO 1962 problem Q1 (#4450)
The problem statement:
Find the smallest natural number $n$ which has the following properties:
(a) Its decimal representation has 6 as the last digit.
(b) If the last digit 6 is erased and placed in front of the remaining digits,
the resulting number is four times as large as the original number $n$.
This is a proof that 153846 is the smallest member of the set satisfying these conditions.
Co-authored-by: Bryan Gin-ge Chen <bryangingechen@gmail.com>
