3
1 5
2 3
3 6

2

#include "bits/stdc++.h"
using namespace std;
#define rep(i, s, n) for(int i=s;i<n;i++)
const int N=10010;
struct se{
    int s,e;
}arr[N];
 
bool cmp(struct se &a,struct se & b){
    return a.e<b.e;
}
int main()
{
    int n;
    while(~scanf("%d",&n)){
        rep(i,0,n)
            scanf("%d%d",&arr[i].s,&arr[i].e);
        sort(arr,arr+n,cmp);
        int cnt=0;
        if(n>0)
        {
            cnt=1;
            
 
int tmp=arr[0].e;
            rep(i,0,n){
                if(arr[i].s>=tmp){
                    cnt++;
                    tmp=arr[i].e;
                }
            }
        }
        printf("%d\n",cnt);
    }
    return 0;
}

51Nod 1133 不重疊的線段 | 典型貪心