20分 dalao求助QAQ

#include<iostream>
#include<queue>
#include<cstdio>
#include<stdio.h>
#include<cstring>
#include<map>
using namespace std;
int n,x,y;
int ans=0;
map<pair<int,int>,bool> m;
pair<int,int> p[1010];
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>x>>y;
		p[i]=make_pair(x,y);
		m[p[i]]=1;
	}
	for(int i=1;i<=n;i++){
		for(int j=1+i;j<=n;j++){
			int dx=p[i].first-p[j].first;
			int dy=p[i].second-p[j].second;
			int x1=p[i].first+dx,y1=p[i].second-dy,x2=p[j].first+dx,y2=p[j].second-dy;
			if(m[make_pair(x1,y1)]&&m[make_pair(x2,y2)])ans++;
			x1=p[i].first-dx,y1=p[i].second+dy,x2=p[j].first-dx,y2=p[j].second+dy;
			if(m[make_pair(x1,y1)]&&m[make_pair(x2,y2)])ans++;
		}
	}
	cout<<ans/4;
    return 0;
}