Question 133
On the board are written initially three consecutive positive integers, $n-1$, $n$, $n+1$. A move consists of choosing two numbers written on the board $a$ and $b$, and replacing them with $2a-b$ and $2b-a$. For what values of $n$ is it possible to obtain, after a succession of such moves, that two of the numbers written on the board are equal to 0?