If no three lines intersect at a point, then every two lines intersect. If any two straight lines of 10 intersect at a point, there is a method of 9+8+7+6+5+4+3+2+ 1, that is, if the two phases intersect at the intersection of 45. However, if nine straight lines intersect at 36 intersections, then eight straight lines will have 28 intersections. There are two straight lines and three intersections left. Take a straight line and intersect with the other two straight lines, and the other straight line intersects with a straight line.