How to write a maple program to calculate the sum of products of polynomial factors missing the factor in the sum?

Question

How to write a maple program to find the sum of the products given below

$\sum\limits_{i=1}^n a_i~\prod\limits_{j=1,j\neq i}^ns-b_j$

Answer 1

program:= (n,a,b,s) -> add(a[i]*mul(s - b[j], j={$1..n} minus {i}), i=1..n);