4
3 6
2 4
0 2
4 7

2

#include<iostream>
#include<algorithm>
using namespace std;
struct xx{
    int s,e;
};
xx a[10005];
int n;
bool cmp(xx x1,xx x2){
    return x1.e<x2.e;
}
int main(){
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>a[i].s>>a[i].e;
    }
    sort(a,a
 
+n,cmp);
    int ss=0,i=1,ans=1;
    while(i<n){
        if(a[ss].e>=a[i].s){
            i++;
            continue;
        }
        if(a[ss].e<a[i].s){
            ans++;
            ss=i;
            i++;
        }
    }
    cout<<ans<<endl;
    return 0;
}

1324：【例6.6】整數區間