On a piece of paper, draw a square with sides equal to n.
Divide the square into n x n equal little squares (call these "cells")
Starting at the leftmost cell in the top row, write in it the figure 1
In the empty cell to the right of the cell you just wrote into, write the value you just wrote plus 1; if there is no empty cell to the right, change your direction of movement to downwards.
Keep moving in the same direction and writing down a number, equal to the one last written plus 1; if there is no empty cell in the direction you were moving, change direction as follows:
If you were moving to the right, change to downwards
If you were moving downwards, change to left
If you were moving to the left, change to upwards
If you were moving up, change to right
Stop when the last number written is equal to n x n
CountZero
"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law