学步园

#include<algorithm>
#include<iostream>
#include<cstdio>
using namespace std;
struct data{
    int s,t;
}a[50001];
inline bool cmp(data a,data b){return a.t<b.t;}
int n;
inline int read(){    
    int x=0,f=1;char ch=getchar();    
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}    
    return x*f;    
}  
int main()
{
	n=read();
    for(int i=1;i<=n;i++){
    	a[i].s=read();a[i].t=read();
    }
    sort(a+1,a+n+1,cmp);
    int end=0,ans=0;
    for(int i=1;i<=n;i++)
    	if(a[i].s>=end){
        	end=a[i].t;
            ans++;
    	}
    printf("%d",ans);
    return 0;
}