#include <fstream>
#include <algorithm>

using namespace std;

ifstream fin("trapez.in");
ofstream fout("trapez.out");

int n,len;
double t[1000005];

struct coord
{
    int x,y;
};
coord v[1005];

inline void Read()
{
    int i;
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>v[i].y>>v[i].x;
    fin.close();
}

inline void Solve()
{
    int i,j,d1,d2,sol=0,k;
    for(i=1;i<=n;i++)
        for(j=1;j<i;j++)
        {
            d1=v[i].x-v[j].x;
            d2=v[i].y-v[j].y;
            if(d2==0)
                t[++len]=(double)485486;
            else
                t[++len]=(double)d1/d2;
        }
    sort(t+1,t+len+1);
    k=1;
    for(i=2;i<=len;i++)
        if(t[i]==t[i-1])
            k++;
        else
        {
            sol+=k*(k-1)/2;
            k=1;
        }
    sol+=k*(k-1)/2;
    fout<<sol<<"\n";
    fout.close();
}

int main()
{
    Read();
    Solve();
    return 0;
}