There is a road about 20klio meters long called "Delin avenue" in GuYuan City Ningxia mountainous area;
在宁夏山区固原市,有一条长约20公里公路叫做“德林大道”;
Ren Delin had extended it to long needle problem, who cancelled the limitation (the diameter of the convex domain is less than the distance of the grid of parallel lines).