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#F1495. Restaurant

    ID: 1501 传统题 2000ms 256MiB 尝试: 0 已通过: 0 难度: 4 上传者: 标签>动态规划贪心排序算法思想编程与模拟进阶难度共享题库Codeforces英文题面题目来源题面语言

Restaurant

题目描述

B. Restaurant
time limit per test
4 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

A restaurant received n orders for the rental. Each rental order reserve the restaurant for a continuous period of time, the i-th order is characterized by two time values − the start time li and the finish time ri (li≤ri).

Restaurant management can accept and reject orders. What is the maximal number of orders the restaurant can accept?

No two accepted orders can intersect, i.e. they can't share even a moment of time. If one order ends in the moment other starts, they can't be accepted both.

Input

The first line contains integer number n (1≤n≤5·105) − number of orders. The following n lines contain integer values li and ri each (1≤li≤ri≤109).

Output

Print the maximal number of orders that can be accepted.

Examples
Input
2
7 11
4 7
Output
1
Input
5
1 2
2 3
3 4
4 5
5 6
Output
3
Input
6
4 8
1 5
4 7
2 5
1 3
6 8
Output
2

题目来源：fps-www.educg.net-codeforce-1-2833.xml.zip；FPS 共享题包，题包内第 1004 题。保留原作者与原赛事署名。