Problem link : Largest Box I can't solve this problem. When I search google for solution I found one solution. In that solution using a formula like this "x = (W+L-sqrt(W*W+L*L-W*L))/6;" How to prove this formula? Solution link : [](http://a-plasma.blogspot.com/2016/01/jans-lightoj-1297-largest-box-solution.html)

Problem Link ,my code here Why I got WA? Please anyone can explain?

Please give some online judge problems in which prefix sum and difference array technique is useful.

Thanks in advance.