Problem Statement

We have $N distinct points on a two-dimensional plane, numbered 1,2,\ldots,N. Point i (1 \leq i \leq N)$ has the coordinates (x_i,y_i).
How many rectangles are there whose vertices are among the given points and whose edges are parallel to the x- or y-axis?

Input

Input is given from Standard Input in the following format:
N
x_1 y_1
x_2 y_2
$\vdots$
x_N y_N

Output

Print the answer.

Constraints

• $4 \leq N \leq 2000$
• $0 \leq x_i, y_i \leq 10^9$
• $(x_i,y_i) \neq (x_j,y_j) (i \neq j)$
• All values in input are integers.

Sample Input 1

6
0 0
0 1
1 0
1 1
2 0
2 1

Sample Output 1

3

There are three such rectangles:
the rectangle whose vertices are Points 1, 2, 3, 4,
the rectangle whose vertices are Points 1, 2, 5, 6,
and the rectangle whose vertices are Points 3, 4, 5, 6.

Sample Input 2

4
0 1
1 2
2 3
3 4

Sample Output 2

0

Sample Input 3

7
0 1
1 0
2 0
2 1
2 2
3 0
3 2

Sample Output 3

1

见题面 Input 部分

见题面 Output 部分