F. Symmetric Projections
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

You are given a set of n points on the plane. A line containing the origin is called good, if projection of the given set to this line forms a symmetric multiset of points. Find the total number of good lines.

Multiset is a set where equal elements are allowed.

Multiset is called symmetric, if there is a point P on the plane such that the multiset is centrally symmetric in respect of point P.

Input

The first line contains a single integer n (1 ≤ n ≤ 2000) — the number of points in the set.

Each of the next n lines contains two integers xi and yi ( - 106  ≤  xi,  yi  ≤  106) — the coordinates of the points. It is guaranteed that no two points coincide.

Output

If there are infinitely many good lines, print -1.

Otherwise, print single integer — the number of good lines.

Examples
Input
31 22 13 3
Output
3
Input
24 31 2
Output
-1
Note

Picture to the first sample test: In the second sample, any line containing the origin is good.