DivInts

Can someone give me some tricky test case or some hint about this task?
I'm still getting 16 out of 20 with my solution:
http://z-trening.com/submit.php?submit=7100094324&subm_code=1

Try to scan dp[] backwards:
...
sort(a, a+n);
last[0]=1100;
for (i=n-1; i>=0; i--) {
...
and some modifications of code.