TADM2E 3.28

We need two pass over X:

1. Calculate cumulative production P and Q:
$ P_0 = 1, P_k=X_k P_{k-1}=\prod_{i=1}^kx_i $
$ Q_n = 1, Q_k=X_k Q_{k+1}=\prod_{i=k}^nx_i $

2. Calculate M:
$ M_k=P_{k-1}Q_{k+1}, k\in[1,n] $