样例多输出了一个

#include<bits/stdc++.h>
using namespace std;
long long n,flag;
struct xy{long long x,y;}a[500001];
bool cmp(xy a1,xy b){return a1.x<b.x||a1.x==b.x&&a1.y>b.y;}
int main(){
	cin>>n;
	for(int i=0;i<n;i++) cin>>a[i].x>>a[i].y;
	sort(a,a+n,cmp);
	for(int i=0;i<n;i++){
		int f=0;
		for(int j=i;j<n;j++){
			if(a[j].x>a[i].x&&a[j].y>a[i].y){
				f++;
				break;
			}
		}
		if(!f){
			if(flag) cout<<",("<<a[i].x<<","<<a[i].y<<")";
			else{
				cout<<"("<<a[i].x<<","<<a[i].y<<")";
				flag++;
			}
		}
	}
	return 0;
}