please solve given DSA question in C$++$:

In a newly planned city, where a city is located at each integral coordinate in a $2-$dimensional plane, there are n Amazon retailers. The i$^($th$)$ retailer residing in the city at the coordinate $($xi$,$ yi$)$ and can deliver to all the cities covered by the rectangle having the $4$ corner points $(0,0),($xi$,0)(0,$ yi$)($xi$,$ yi$)$ We say that a point $($a$,$ b$)$ is covered by a rectangle if it lies inside the rectangle or on its boundaries. Note that no $2$ retailers reside in the same city.

Given q requests of the form $($a$,$ b$)$ determine the number of retailers who can deliver to the city at the coordinate $($a$,$ b$)$