MathNet 2012 Question 54

Let $(a_n)_{n\ge1}$ be an increasing bounded sequence. Calculate the limit of the cyclic product $$\lim_{n\to\infty}\left[\prod_{j=1}^{n-2}(2a_n-a_j-a_{j+1})\right](2a_n-a_{n-1}-a_1).$$