Author:  A. Baranov  Time limit:  1 sec  
Input file:  Standard input  Memory limit:  512 Mb  
Output file:  Standard output 
Consider a set of N twodimensional points represented by their coordinates (X_{i}, Y_{i}).
It is required to determine the number of all possible rectangles that satisfy the following conditions:
Input starts with integer N,
followed by 2 × N integers, representing point coordinates: X_{i}, Y_{i}.
The output should contain
the number of detected rectangles.
All input points are different.
− 10^{6} ≤ (X_{i}, Y_{i}) ≤ 10^{6},
4 ≤ N ≤ 10^{5}
No.  Standard input  Standard output 

1 


2 

