Attain the Number of Points From SquareGrid

I am one step away from finishing a script for random height buildings generated on a grid across a rectangular surface. The "N" in the Random module is the variation of building heights, and I want that to match the number of points on the grid, which is given by "P" if the SquareGrid module. However, whenever I try dragging from P to N, it inputs the list that P represents, rather than the number of points. I have tried several other commands, and after an hour of no progress, I decided to ask this community for help!
I am new to Grasshopper, so please bare with me! Thank you!