【CodeForces】597B - Restaurant（贪心）

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. 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

经典的贪心算法的题，和hdu的《今年暑假不AC》一样。

代码如下：

#include <cstdio>
#include <algorithm>
using namespace std;
struct node
{
	int st,endd;
}data[500000+11];
bool cmp(node a,node b)
{
	return a.endd < b.endd;
}
int main()
{
	int n;
	while (~scanf ("%d",&n))
	{
		for (int i = 0 ; i < n ; i++)
			scanf ("%d %d",&data[i].st,&data[i].endd);
		sort(data,data+n,cmp);
		int pos = 0;
		int ans = 1;
		for (int i = 1 ; i < n ; i++)
		{
			if (data[i].st > data[pos].endd)
			{
				pos = i;
				ans++;
			}
		}
		printf ("%d\n",ans);
	}
	return 0;
}