দাবা নিয়ে দাবাদাবি

[nargisakter1572]

https://gonitzoggo.com/archive/problem/145
Please help me to solve it.

[ferojkabirnh9]

For N×N grid number of rectangle is
(n^2)(n+1)^2/4

[nargisakter1572]

Thanks to you. I have been able to solve it by your hint.