I - Restaurant

- Restaurant

Time Limit:4000MS     Memory Limit:262144KB     64bit IO Format:%I64d & %I64u

Submit  Status

Description

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_ieach (1 ≤ l_i ≤ r_i ≤ 10⁹).

Output

Print the maximal number of orders that can be accepted.

Sample Input

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

本题为贪心

代码：

#include<stdio.h>
#include<algorithm>
using namespace std;
#define MAX 500000+10
struct node
{
	int l;
	int r;
}a[MAX];
int cmp(node x,node y)
{
	return x.r<y.r;
}
int main()
{
	int n,t;
	scanf("%d",&n);
	for(int i=0;i<n;i++)
	{
		scanf("%d %d",&a[i].l,&a[i].r);
	}
	sort(a,a+n,cmp);
	int ans=1;
	t=a[0].r;
	for(int i=1;i<n;i++)
	{
		if(a[i].l>t)
		{
			ans++;
			t=a[i].r;
		}
	}
	printf("%d\n",ans);
	return 0;
}