# Given an array \$a\$, we have to find product of \$a_{j}\$-\$a_{i}\$ modulo \$998244353\$ over all \$i\$ and \$j\$ given \$j>i\$

Given an array $$a$$, we have to find product of $$a_{j}$$$$a_{i}$$ modulo $$998244353$$ over all $$i$$ and $$j$$ given $$j>i$$.
For eg. Let the array be $$1,2,3$$ then my answer will be calculated as-
$$(2-1)$$.$$(3-1)$$.$$(3-2)$$=$$2$$
As number of elements in the array could be large (upto $$10^5$$) I am looking for solution of order $$nlogn$$.
I have tried representing array as a polynomial but could get anything out of it. Please help.