CF597B.Restaurant

普及/提高-

通过率：0%

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题目描述

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 $l_{i}$ and the finish time $r_{i}$ ( $l_{i}<=r_{i}$ ).

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.

输入格式

The first line contains integer number $n$ ( $1<=n<=5·10^{5}$ ) — number of orders. The following $n$ lines contain integer values $l_{i}$ and $r_{i}$ each ( $1<=l_{i}<=r_{i}<=10^{9}$ ).

输出格式

Print the maximal number of orders that can be accepted.

输入输出样例

输入#1
```
2
7 11
4 7
```
输出#1
```
1
```
输入#2
```
5
1 2
2 3
3 4
4 5
5 6
```
输出#2
```
3
```
输入#3
```
6
4 8
1 5
4 7
2 5
1 3
6 8
```
输出#3
```
2
```

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