smc

First, write a few terms of the sequence: $1,3,2,-1,-3,-2,1,3,2,\dots$ Notice how the pattern repeats every six terms and every six terms have a sum of 0. Then, find that the $16\ast 6=96$th term is $-2$ and the sum of the all those previous terms is $0$. Then, write the 97th to the 100th terms down: $1,3,2,-1$ and add them up to get the sum of $\boxed{5}$