#include<cstdio>

#include<map>

//#include<bits/stdc++.h>

#include<vector>

#include<stack>

#include<iostream>

#include<algorithm>

#include<cstring>

#include<cmath>

#include<queue>

#include<cstdlib>

#include<climits>

#define PI acos(-1.0)

#define INF 0x3f3f3f3f

using namespace std;

typedef long long ll;

typedef pair<double,double> pdd;

typedef __int64 int64;

const ll mood=1e9+;

const int64 Mod=;

const double eps=1e-;

const int N=2e7+;

const int MAXN=;

inline void rl(ll&num){

    num=;ll f=;char ch=getchar();

    while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}

    while(ch>=''&&ch<='')num=num*+ch-'',ch=getchar();

    num*=f;

}

inline void ri(int &num){

    num=;int f=;char ch=getchar();

    while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}

    while(ch>=''&&ch<='')num=num*+ch-'',ch=getchar();

    num*=f;

}

double a[MAXN],b[MAXN];

int main()

{

    int n;

    map<pdd,int>mp;

    ri(n);

    for(int i=;i<n;i++)

    {

        scanf("%lf%lf",&a[i],&b[i]);

    }

    pdd x;

    for(int i=;i<n;i++)

    {

        for(int j=i+;j<n;j++)

        {

            x.first=(a[i]+a[j])/;

            x.second=(b[i]+b[j])/;

            mp[x]++;

        }

    }

    ll ans=;

    map<pdd,int>::iterator it;

    for(it=mp.begin();it!=mp.end();++it)

    {

        int tem=it->second;

        pdd t=it->first;

        ans+=(tem-)*tem/;

    }

    cout<<ans<<endl;

    return ;

}