#include <iostream>#include <algorithm>#include <stdio.h>using namespace std;const int N=2002;struct m_point{ int x,y;};int n;m_point p[N];bool cmp(const m_point &p1,const m_point &p2){ if(p1.x < p2.x) return true; if((p1.x == p2.x) && (p1.y < p2.y)) return true; return false;}bool find_point(m_point &t){ int left=0,right=n,mid; while(left<=right) { mid=(left+right)>>1; if((p[mid].x == t.x) && (p[mid].y == t.y)) return true; if(cmp(t,p[mid])) right=mid-1; else left=mid+1; } return false;}int main(){ int i,j,ans; m_point tmp,new_node; while(scanf("%d",&n) != EOF) { for(i=0;i<n;++i) scanf("%d%d",&p[i].x,&p[i].y); sort(p,p+n,cmp); ans=0; for(i=0;i<n;++i) { for(j=i+1;j<n;++j) { tmp.x=p[j].x-p[i].x; tmp.y=p[j].y-p[i].y; new_node.x=p[i].x+tmp.y; new_node.y=p[i].y-tmp.x; if(!find_point(new_node)) continue; new_node.x=p[j].x+tmp.y; new_node.y=p[j].y-tmp.x; if(!find_point(new_node)) continue; ++ans; } } printf("%dn",ans/2); } return 0;}
