AtCoder Grand Contest 015
E
Mr.Aoki Incubator
AtCoder
⌀ 3571
原题
← DF →
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Problem Statement

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Takahashi is an expert of Clone Jutsu, a secret art that creates copies of his body.

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On a number line, there are $N$ copies of Takahashi, numbered $1$ through $N$. The $i$-th copy is located at position $X_i$ and starts walking with velocity $V_i$ in the positive direction at time $0$.

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Kenus is a master of Transformation Jutsu, and not only can he change into a person other than himself, but he can also transform another person into someone else.

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Kenus can select some of the copies of Takahashi at time $0$, and transform them into copies of Aoki, another Ninja. The walking velocity of a copy does not change when it transforms. From then on, whenever a copy of Takahashi and a copy of Aoki are at the same coordinate, that copy of Takahashi transforms into a copy of Aoki.

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Among the $2^N$ ways to transform some copies of Takahashi into copies of Aoki at time $0$, in how many ways will all the copies of Takahashi become copies of Aoki after a sufficiently long time? Find the count modulo $10^9+7$.

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Constraints

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  • $1 ≤ N ≤ 200000$
  • $1 ≤ X_i,V_i ≤ 10^9(1 ≤ i ≤ N)$
  • $X_i$ and $V_i$ are integers.
  • All $X_i$ are distinct.
  • All $V_i$ are distinct.
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Input

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The input is given from Standard Input in the following format:

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N
X_1 V_1
:
X_N V_N

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Output

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Print the number of the ways that cause all the copies of Takahashi to turn into copies of Aoki after a sufficiently long time, modulo $10^9+7$.

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样例

Input #1
3
2 5
6 1
3 7
Output #1
6
All copies of Takahashi will turn into copies of Aoki after a sufficiently long time if Kenus transforms one of the following sets of copies of Takahashi into copies of Aoki: $(2)$, $(3)$, $(1,2)$, $(1,3)$, $(2,3)$ and $(1,2,3)$.
Input #2
4
3 7
2 9
8 16
10 8
Output #2
9
题目信息
题号
agc015_e
时间限制
2 s
内存限制
256 MB

题面与样例版权归 AtCoder 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。