Input
The first line contains one number N (3≤N≤100000). Next, N lines contain a pair of numbers – coordinates of the next vertex of a simple polygon in clockwise or counterclockwise order.
Imprint
Print one line: “YES”, if the given polygon is convex, and “NO” otherwise.
Examples
| # |
Input |
Output |
| 1 |
3
0 0
0 1
10 |
YES |
| 2 |
6
0 0
0 2
1 2
1 1
2 1
20 |
NO |