You can also compress the coordinates and use a normal BIT, which would be much easier.
A couple of hours into the contest, I was much more calm and poised. And for some reason, day 2 of the contest was also much better than day 1.
I had the same exact situation I guess. I think I got really tensed on Day 1 because of which I couldn't solve a really easy problem, but I performed much better on Day 2.