Figure 4
(a) Pavement of a pedestrian street, (b) the coordinate system for the rectangle tiles. Every original \(4\times 4\) square is divided either into U–D pair or into L–R pair. The integers on the axes skip multiples of 4; e.g. tiles with \(x\equiv 2\pmod 4\), \(y\equiv 3\pmod 4\) are U tiles, etc. (c) The coordinate axes and the unit, the coordinates assigned to the tiles are the Cartesian coordinates of their midpoints.
