| Nộp bài | Các bài nộp | Làm tốt nhất | Về danh sách bài |
HINHTHOI - Hình thoi |
| English | Vietnamese |
Rhombs
A rhomb is a four-sided polygon in which every side has the same length. The rhomb shape appears in the diamonds suit in playing cards, in art patterns, etc. Squares are also special cases of rhombs.
You have to solve a problem about rhombs: given N points in the plane, count the number of rhombs which have four verticles in the given set of points.
Input
- Line 1: a number N that is the number of points (4 ≤ N ≤ 1500).
- The ith line of the next N lines contains two integers xi, yi that are coordinates of the ith point (-50 ≤ xi, yi ≤ 50).
Output
Print a single number that is the number of rhombs that have four verticles in the given set of points.
Example
Input 8 -1 0 0 1 1 0 0 0 1 1 0 -1 1 -1 2 0 Output 4
| Được gửi lên bởi: | VOJ Team |
| Ngày: | 2008-08-20 |
| Thời gian chạy: | 0.100s-1s |
| Giới hạn mã nguồn: | 50000B |
| Memory limit: | 1536MB |
| Cluster: | Cube (Intel G860) |
| Ngôn ngữ cho phép: | ADA95 ASM32 BASH BF C CSHARP CPP C99 CLPS LISP sbcl LISP clisp D FORTRAN HASK ICON ICK JAVA LUA NEM NICE OCAML PAS-GPC PAS-FPC PERL PHP PIKE PRLG-swi PYTHON RUBY SCM guile SCM qobi ST TEXT WHITESPACE |
| Nguồn bài: | VNOI Marathon '08 - Round 10/DivA Problem Setter: Ngô Minh Đức |
