Restaurant （背包问题）

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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, thei-th order is characterized by two time values — the start timel_i and the finish timer_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 followingn 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

27 114 7

Output

1

Input

51 22 33 44 55 6

Output

3

Input

64 81 54 72 51 36 8

Output

2

题解：这是背包问题，直接做就可以

下面是我的代码：

#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;}