# Count 'em Staircases (Count 'em All 16!)

A staircase grid is a grid of squares that resembles a staircase shape, for example, the figure below shows 4 staircase grids with dimensions $$1\times1$$, $$2\times2$$, $$3\times3$$, $$4\times4$$ respectively.

Count the total number of quadrilaterals in a $$30\times 30$$ staircase grid (that is, when $$a=30$$).

Clarification: A quadrilateral is a polygon that has 4 sides.

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