1 #include<iostream>
 2 #include<algorithm>
 3 using namespace std;
 4 long long x[10010],y[10001];
 5 struct sb
 6 {
 7     long long x,y,xx;
 8 }tmp[10001];
 9 void turn(int p)
10 {
11     swap(tmp[p].x,tmp[p].y);
12     tmp[p].y=-tmp[p].y;
13     tmp[p].xx=(tmp[p].xx+1)%4;
14 }
15 bool cmp(sb a,sb b)
16 {
17     return a.x*b.y>b.x*a.y;
18 }
19 int cnt;
20 int main ()
21 {
22     int n;
23     cin>>n;
24     for (int i=1;i<=n;i++) cin>>x[i]>>y[i];
25     for (int i=1;i<=n;i++)
26     {
27         for (int j=1;j<=n;j++)
28         {
29             tmp[j].x=x[j]-x[i];
30             tmp[j].y=y[j]-y[i];
31             tmp[j].xx=0;
32             if (i==j)
33             {
34                 tmp[j].x=tmp[1].x;
35                 tmp[j].y=tmp[1].y;
36                 tmp[j].xx=tmp[1].xx;
37             }
38             else 
39               while (tmp[j].x<=0||tmp[j].y<0) turn(j);
40         }
41         sort(tmp+2,tmp+n+1,cmp);
42         int j=2;
43         while (j<=n)
44         {
45             int ans[4]={0};
46             int k=j;
47             while (k<=n&&tmp[j].x*tmp[k].y==tmp[k].x*tmp[j].y)
48                 ans[tmp[k].xx]++,k++;
49             for (int kk=0;kk<=3;kk++)
50               cnt+=ans[kk]*ans[(kk+1)%4];
51             j=k; 
52         }
53     }
54     cout<<cnt;
55 }