\(2^{nd}\) round, November \(8^{th}\), 2014
Little Bob is a famous builder. He bought land and wants to build a house. Unfortunately, the problem is the
land’s terrain, it has a variable elevation.
The land is shaped like a rectangle, N meters wide and M meters long. It can be divided into \(N \cdot M\) squares
(see the image). Bob’s house will be shaped like a rectangle that has sides parallel with the land’s edges and
its vertices coincide with the vertices of the squares. All the land covered by Bob’s house must be of equal
elevation to prevent it from collapsing.
2
2
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1
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1
2
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The land divided into squares.
Two possible locations \(of\) house are marked with red and blue.
Calculate the number of ways Bob can build his house!

In test cases worth 20% of total points, it will hold N, M ⩽50.
In test cases worth 60% of total points, it will hold N, M ⩽500.

The first line of input contains integers N and M (1 ⩽N, M ⩽1 000).
Each of the following N lines contains M integers a_{ij} (1 ⩽a_{ij} ⩽\(10^{9}\)), respectively the height of each square of
land.
Warning: Please use faster input methods beacuse the amount of input is very large. (For example, use scanf
instead of cin in C++ or BufferedReader instead of Scanner in Java.)

The first and only line of output must contain the required number from the task statement.

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출처 COCI 2014/2015 Contest 2