You are given a checkerboard with
Modify: Given the row and column of a square on the checkerboard,
change the number written in it to a new value.
Query: Given the coordinates of two squares on the checkerboard, find
the alternating sum of all of the numbers within the rectangle delimited
by those two squares. By alternating sum what is meant is that we add
all numbers in squares with the same colour as the first square given,
and subtract all numbers with the opposite colour.
Input Specification
The first line of the input file contains the integers
A number of input lines then follow. The integer at the beginning of the
line signifies:
There will never be more than
Output Specification
For each query operation, print the answer on its own line.
Sample Input
3 3
1 1 2 5
1 3 1 -2
2 1 1 2 3
1 2 3 11
2 2 1 3 3
0
Sample Output
-5
13
Sample Explanation
The checkerboard is three cells by three cells. When the first query is executed, the board looks like this:
0 5 0
0 0 0
-2 0 0
We are asked to find the alternating sum of the first two rows. Since
the
0 5 0
0 0 11
-2 0 0
Now, we take the alternating sum of the second and third rows.
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