WolfCarpet | Topcoder Archive

Problem Statement

Cat Snuke has a carpet of infinite size. The carpet is split into square cells. The top left cell has coordinates (0,0), and the cell in row i and column j has coordinates (i,j).

If either i or j is even, cell (i,j) is painted black; otherwise, it's painted white.

Wolf Sothe will buy a rectangular section of Snuke's carpet. The top left cell of this section is (r1,c1) and its bottom right cell is (r2,c2).

You're given ints r1, c1, r2 and c2. Compute and return the number of black cells in the rectangle that Sothe will buy.

Definition

Class:: WolfCarpet
Method:: count
Parameters:: int, int, int, int
Returns:: long
Method signature:: long count(int r1, int c1, int r2, int c2)
(be sure your method is public)

Constraints

r1 will be between 0 and 1,000,000,000, inclusive.
c1 will be between 0 and 1,000,000,000, inclusive.
r2 will be between r1 and 1,000,000,000, inclusive.
c2 will be between c1 and 1,000,000,000, inclusive.

Examples

```
1
```
```
1
```
```
2
```
```
3
```
```
Returns: 4
```
Cells (1,2), (2,1), (2,2) and (2,3) are painted black.
```
0
```
```
0
```
```
0
```
```
10
```
```
Returns: 11
```
All cells in the rectangle are located in even rows, so they are all painted black.
```
1
```
```
1
```
```
1
```
```
1
```
```
Returns: 0
```
Cell (1,1) is white, so no cells in the rectangle are painted black.
```
5
```
```
12
```
```
40
```
```
26
```
```
Returns: 414
```

1000000000

1000000000

Returns: 750000002000000001

81695509

209408464

949118329

220137366

Returns: 6979871694045002

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