#include <cstdio>
#include <algorithm>
#define abs(x)((x)<0 ? -(x) : (x))
#define EPS 0.0000000001
#define maxN 1005
using namespace std;
struct punct
{
    double x, y;
}v[maxN];
int n, i, j, k, nr;
double p;
bool cmp(punct a, punct b)
{
    if(abs(a.x-b.x) <= EPS) return a.y < b.y;
    else return a.x < b.x;
}
bool CB(punct a)
{
    int st=1, dr=n, mij;
    while(st <= dr)
    {
        mij = (st+dr)>>1;
        if(abs(v[mij].x-a.x) <= EPS && abs(v[mij].y-a.y) <= EPS)
            return true;
        if(cmp(a, v[mij]))
            dr = mij-1;
        else st = mij+1;
    }
    return false;
}
int main()
{
    freopen("patrate3.in", "r", stdin);
    freopen("patrate3.out", "w", stdout);
    scanf("%d", &n);
    for(i = 1; i <= n; i++)
        scanf("%lf %lf", &v[i].x, &v[i].y);
    sort(v+1, v+n+1, cmp);
    for(i = 1; i < n; i++)
        for(j = i+1; j <= n; j++)
    {
        punct v1, v2;
        v1.x = v[i].x + v[i].y - v[j].y;
        v1.y = v[i].y + v[j].x - v[i].x;
        v2.x = v[j].x + v[i].y - v[j].y;
        v2.y = v[j].y + v[j].x - v[i].x;
        if(CB(v1) && CB(v2)) nr++;
    }
    printf("%d", nr/2);
    return 0;
}