ZOJ Problem Set - 2499
The Happy Worm lives in an m*n rectangular field. There are k stones placed in certain locations of the field. (Each square of the field is either empty, or contains a stone.) Whenever the worm sleeps, it lies either horizontally or vertically, and stretches so that its length increases as much as possible. The worm will not go in a square with a stone or out of the field. The happy worm can not be shorter than 2 squares.
The question you are to answer is how many different positions this worm could be in while sleeping.
The first line of the input file contains a single integer t (1 <= t <= 11), the number of test cases, followed by the input data for each test case. The first line of each test case contains three integers m, n, and k (0 <= m,n,k <= 200000). The input for this test case will be followed by k lines. Each line contains two integers which specify the row and column of a stone. No stone will be given twice.
There should be one line per test case containing the number of positions the happy worm can be in.
1 5 5 6 1 5 2 3 2 4 4 2 4 3 5 1
Source: Asia 2004, Tehran (Iran), Sharif Preliminary