1234 -> 2002 - All-Russian MO 2002 Regional (R4) 8.5
Source:
September 17, 2024
combinatoricsnumber theory
Problem Statement
The four-digit number written on the board can be replaced by another, adding one to its two adjacent digits, if neither of these digits is not equal to ; or, subtracting one from the adjacent two digits, if none of them is equal to . Is it possible using such operations from does the number get the number ?