Codeforces Round 523 (Div. 2)
D
TV Shows
Codeforces
2000
原题
← CE →
翻译中…

There are $n$ TV shows you want to watch. Suppose the whole time is split into equal parts called "minutes". The $i$-th of the shows is going from $l_i$-th to $r_i$-th minute, both ends inclusive.

翻译中…

You need a TV to watch a TV show and you can't watch two TV shows which air at the same time on the same TV, so it is possible you will need multiple TVs in some minutes. For example, if segments $[l_i, r_i]$ and $[l_j, r_j]$ intersect, then shows $i$ and $j$ can't be watched simultaneously on one TV.

翻译中…

Once you start watching a show on some TV it is not possible to "move" it to another TV (since it would be too distracting), or to watch another show on the same TV until this show ends.

翻译中…

There is a TV Rental shop near you. It rents a TV for $x$ rupees, and charges $y$ ($y \lt x$) rupees for every extra minute you keep the TV. So in order to rent a TV for minutes $[a; b]$ you will need to pay $x + y \cdot (b - a)$.

翻译中…

You can assume, that taking and returning of the TV doesn't take any time and doesn't distract from watching other TV shows. Find the minimum possible cost to view all shows. Since this value could be too large, print it modulo $10^9 + 7$.

翻译中…

Input

翻译中…

The first line contains integers $n$, $x$ and $y$ ($1 \le n \le 10^5$, $1 \le y \lt x \le 10^9$) — the number of TV shows, the cost to rent a TV for the first minute and the cost to rent a TV for every subsequent minute.

翻译中…

Each of the next $n$ lines contains two integers $l_i$ and $r_i$ ($1 \le l_i \le r_i \le 10^9$) denoting the start and the end minute of the $i$-th TV show.

翻译中…

Output

翻译中…

Print exactly one integer — the minimum cost to view all the shows taken modulo $10^9 + 7$.

翻译中…

Note

翻译中…

In the first example, the optimal strategy would be to rent $3$ TVs to watch:

翻译中…
  • Show $[1, 2]$ on the first TV,
  • Show $[4, 10]$ on the second TV,
  • Shows $[2, 4], [5, 9], [10, 11]$ on the third TV.
翻译中…

This way the cost for the first TV is $4 + 3 \cdot (2 - 1) = 7$, for the second is $4 + 3 \cdot (10 - 4) = 22$ and for the third is $4 + 3 \cdot (11 - 2) = 31$, which gives $60$ int total.

翻译中…

In the second example, it is optimal watch each show on a new TV.

翻译中…

In third example, it is optimal to watch both shows on a new TV. Note that the answer is to be printed modulo $10^9 + 7$.

翻译中…

样例

Input #1
5 4 3
1 2
4 10
2 4
10 11
5 9
Output #1
60
InputCopy OutputCopy
Input #2
6 3 2
8 20
6 22
4 15
20 28
17 25
20 27
Output #2
142
InputCopy OutputCopy
Input #3
2 1000000000 2
1 2
2 3
Output #3
999999997
InputCopy OutputCopy
题目信息
题号
1061D
时间限制
2 s
内存限制
256 MB
标签
数据结构
贪心
模拟
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。