codeforces 597B Restaurant

B. 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.

Sample test(s)

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

#include<cstdio>
#include<algorithm>
using namespace std;
struct order
{
    int l,r;
}r[500005];
bool cmp(order a,order b)
{
    return a.r<b.r;
}
int main()
{
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++)
        scanf("%d%d",&r[i].l,&r[i].r);
    sort(r,r+n,cmp);
    int e=r[0].r,ans=1;
    for(int i=1;i<n;i++)
        if(e<r[i].l)
        {
            ans++;
            e=r[i].r;
        }
    printf("%d\n",ans);
    return 0;
}