Codeforces Round 329 (Div. 2)
B
Anton and Lines
Codeforces
1600
原题
← AC →
翻译中…

The teacher gave Anton a large geometry homework, but he didn't do it (as usual) as he participated in a regular round on Codeforces. In the task he was given a set of $*n*$ lines defined by the equations $*y* = *k*_{*i*}·*x* + *b*_{*i*}$. It was necessary to determine whether there is at least one point of intersection of two of these lines, that lays strictly inside the strip between $*x*_{1} < *x*_{2}$. In other words, is it true that there are $1 ≤ *i* < *j* ≤ *n*$ and $*x*', *y*'$, such that:

翻译中…
  • $*y*' = *k*_{*i*} * *x*' + *b*_{*i*}$, that is, point $(*x*', *y*')$ belongs to the line number $*i*$;
  • $*y*' = *k*_{*j*} * *x*' + *b*_{*j*}$, that is, point $(*x*', *y*')$ belongs to the line number $*j*$;
  • $*x*_{1} < *x*' < *x*_{2}$, that is, point $(*x*', *y*')$ lies inside the strip bounded by $*x*_{1} < *x*_{2}$.
翻译中…

You can't leave Anton in trouble, can you? Write a program that solves the given task.

翻译中…

Input

翻译中…

The first line of the input contains an integer $*n*$ ($2 ≤ *n* ≤ 100 000$) — the number of lines in the task given to Anton. The second line contains integers $*x*_{1}$ and $*x*_{2}$ ($- 1 000 000 ≤ *x*_{1} < *x*_{2} ≤ 1 000 000$) defining the strip inside which you need to find a point of intersection of at least two lines.

翻译中…

The following $*n*$ lines contain integers $*k*_{*i*}$, $*b*_{*i*}$ ($- 1 000 000 ≤ *k*_{*i*}, *b*_{*i*} ≤ 1 000 000$) — the descriptions of the lines. It is guaranteed that all lines are pairwise distinct, that is, for any two $*i* ≠ *j*$ it is true that either $*k*_{*i*} ≠ *k*_{*j*}$, or $*b*_{*i*} ≠ *b*_{*j*}$.

翻译中…

Output

翻译中…

Print "Yes" (without quotes), if there is at least one intersection of two distinct lines, located strictly inside the strip. Otherwise print "No" (without quotes).

翻译中…

Note

翻译中…

In the first sample there are intersections located on the border of the strip, but there are no intersections located strictly inside it.

翻译中…

image

翻译中…

样例

Input #1
4
1 2
1 2
1 0
0 1
0 2
Output #1
NO
InputCopy OutputCopy
Input #2
2
1 3
1 0
-1 3
Output #2
YES
InputCopy OutputCopy
Input #3
2
1 3
1 0
0 2
Output #3
YES
InputCopy OutputCopy
Input #4
2
1 3
1 0
0 3
Output #4
NO
InputCopy OutputCopy
题目信息
题号
593B
时间限制
1 s
内存限制
256 MB
标签
计算几何
排序

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。