Restaurant （揹包問題）

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                                    Restaurant

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.

Input

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

Output

Print the maximal number of orders that can be accepted.

Example

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

題解：這是揹包問題，直接做就可以

下面是我的代碼：

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<iostream>
using namespace std;
struct P
{
	int star;
	int endd;
}num[900000];
bool cmp(P a,P b)
{
	return a.endd<b.endd;
}
int main()
{
	int n,k,p;
	while(scanf("%d",&n)!=EOF)
	{
		k=1;
		for(int i=0;i<n;i++)
		{
			scanf("%d%d",&num[i].star,&num[i].endd);
		}
		sort(num,num+n,cmp);
		p=num[0].endd;
		for(int i=1;i<n;i++)
		{
			if(num[i].star>p)
			{
				k++;
				p=num[i].endd;
			}
		}
		printf("%d\n",k);
	}
	return 0;
}