Nguồn: http://codeforces.com
Today, Wet Shark is given n bishops
on a 1000 by 1000 grid. Both rows and columns
of the grid are numbered from 1 to 1000. Rows are
numbered from top to bottom, while columns are numbered from left to right.
Wet Shark thinks that two bishops attack each other if
they share the same diagonal. Note, that this is the only criteria, so two
bishops may attack each other (according to Wet Shark) even if there is another
bishop located between them. Now Wet Shark wants to count the number of pairs
of bishops that attack each other.
Input
The first line of the input contains n (1 ≤ n ≤ 200 000) — the
number of bishops.
Each of next n lines
contains two space separated integers xi and yi (1 ≤ xi, yi ≤ 1000) — the
number of row and the number of column where i-th bishop is
positioned. It's guaranteed that no two bishops share the same position.
Output
Output one integer — the number of pairs of
bishops which attack each other.
Examples
|
Input
|
Output
|
|
Input
|
Output
|
|
5
1 1 1 5 3 3 5 1 5 5 |
6
|
|
3
1 1 2 3 3 5 |
0
|
Note
In the first sample following pairs of bishops attack each
other: (1, 3), (1, 5), (2, 3), (2, 4), (3, 4) and (3, 5). Pairs (1, 2), (1, 4), (2, 5)and (4, 5) do not
attack each other because they do not share the same diagonal.
Tóm
tắt đề:
Cho N con tượng đứng trên bàn cờ kích thước 1000 x 1000. Hỏi có
bao nhiêu cặp
tượng ăn nhau ?
tượng ăn nhau ?
