#include<bits/stdc++.h>
#pragma GCC optimize("Ofast,no-stack-protector")
using namespace std;
#define int long long
constexpr double eps=1e-8;
constexpr double PI=acos(-1.0);
int sgn(double x){
  if(fabs(x)<eps)return 0;
  if(x>0)return 1;return -1;
}
struct Point{
  double x,y;
  Point(){}
  Point(double _x,double _y):x(_x),y(_y){}
  Point operator-(const Point&b)const{return(Point){x-b.x,y-b.y};}
  Point operator+(const Point&b)const{return(Point){x+b.x,y+b.y};}
  double operator^(const Point&b)const{return x*b.y-y*b.x;}
  double operator*(const Point&b)const{return x*b.x+y*b.y;}
  bool operator<(const Point&b)const{return x<b.x||(x==b.x&&y<b.y);}
  bool operator==(const Point&b)const{return sgn(x-b.x)==0&&sgn(y-b.y)==0;}
  Point rotate(double B,Point P){return(Point){(x-P.x)*cos(B)-(y-P.y)*sin(B)+P.x,(x-P.x)*sin(B)+(y-P.y)*cos(B)+P.y};}
};
double dist(Point a,Point b){return sqrt((a-b)*(a-b));}
double len(Point a){return sqrt(a.x*a.x+a.y*a.y);}
Point p[2010],ch[2010];int vis[2010];
void ConvexHull(Point *p,int n,Point *ch){
  sort(p,p+n),n=unique(p,p+n)-p;
  int m=0,k;
  stack<int>ans;
  for(int i=0;i<n;++i){
    while(m>1&&sgn((ch[m-1]-ch[m-2])^(p[i]-ch[m-1]))<=0)--m,ans.pop();
    ch[m++]=p[i],ans.push(i);
  }k=m;
  for(int i=n-2;i>=0;--i){
    while(m>k&&sgn((ch[m-1]-ch[m-2])^(p[i]-ch[m-1]))<=0)--m,ans.pop();
    ch[m++]=p[i],ans.push(i);
  }if(n>1)--m,ans.pop();
  while(!ans.empty())vis[ans.top()]=1,ans.pop();
}
unordered_map<int,int>mp;
inline int getpoint(double x,double y){return (x+1000001)*2000001+y;}
inline int getpoint(Point i){return getpoint(i.x,i.y);}
Point C,P[2010];
bool cmp(Point a,Point b){
  a=a-C,b=b-C;
  if(atan2(a.y,a.x)!=atan2(b.y,b.x))
    return atan2(a.y,a.x)<atan2(b.y,b.x);
  else return a.x<b.x;
}
signed main(){
  int n,ans=0;cin>>n;
  for(int i=0;i<n;++i)cin>>p[i].x>>p[i].y;
  ConvexHull(p,n,ch);
  for(int i=0;i<n;++i)if(vis[i])mp[getpoint(p[i])]=1;
  for(int i=0;i<n;++i)if(!mp.count(getpoint(p[i]))){
    int cnt=0;for(int j=0;j<n;++j)if(j!=i)P[cnt++]=p[j];
    C=p[i];sort(P,P+cnt,cmp);
    //for(int j=0;j<cnt;++j)cout<<P[j].x<<' '<<P[j].y<<endl;
    //cout<<endl;
    for(int j=0;j<cnt;++j)if(mp.count(getpoint(P[j]))&&mp.count(getpoint(P[(j+1)%cnt])))
      ++ans;//cout<<p[i].x<<' '<<p[i].y<<' '<<P[j].x<<' '<<P[j].y<<' '<<P[(j+1)%cnt].x<<' '<<P[(j+1)%cnt].y<<endl;
  }
  cout<<ans+1<<endl;
  return 0;
}