#include<fstream>
#include<algorithm>
#define dim 1006
using namespace std;
ifstream f("trapez.in");
ofstream g("trapez.out");
struct  cub
{
    int x,y;
}
v[dim];
double p[dim*dim];
int i,n,j,sub,sol,nr;
double a,b;
int main ()  
{
    f>>n;
    for(i=1;i<=n;++i)
	{
        f>>v[i].x>>v[i].y;
    }
    for(i=1;i<n;++i) 
	{ 
        for(j=i+1;j<=n;++j){
            a=(v[j].x-v[i].x);
            b=(v[j].y-v[i].y);
            p[++nr]=(double)(a/b);
        }
    }
    sort(p+1,p+1+nr);
    for(i=1;i<=nr;++i) 
	{
        sub=1;
        while(i<nr && p[i+1]==p[i]) 
		{
            ++i;
            sub++;
        }
        sol+=sub*(sub-1)/2;
    }
    g<<sol<<"\n";
    return 0;
}