Covering#1348
A large rectangle with sides parallel to the coordinate axes is given, with non-adjacent vertices at and . Inside it, there are smaller rectangles, also with sides parallel to the axes, specified by their non-adjacent vertices. The coordinates of the -th rectangle are non-negative integers: (a_i, b_i) and (c_i, d_i).
Find the area of the largest rectangle that is not covered by the placed small rectangles.
The first line contains , , (1 \le n, m \le 10000, 1 \le k \le 100) — the size of the large rectangle and the number of smaller rectangles inside it.
Each of the next lines contains the coordinates of a small rectangle: 0 \le a_i, c_i \le n, 0 \le b_i, d_i \le m.
Print the area of the largest rectangle not covered by any of the given small rectangles.
Example 1