#include<bits/stdc++.h>
#define fi first
#define se second
using namespace std;
const int N=1e3;
struct Point
{
long long x,y;
};
Point operator-(Point a,Point b)
{
return {a.x-b.x,a.y-b.y};
}
long long operator*(Point a,Point b)
{
return a.x*b.y-a.y*b.x;
}
int sgn(long long x)
{
return (x<0 ? -1:1);
}
int ilo(Point a,Point b,Point c)
{
return sgn((a-c)*(b-c));
}
bool cross(Point a,Point b,Point c,Point d)
{
return (ilo(c,b,a)!=ilo(d,b,a) && ilo(a,d,c)!=ilo(b,d,c));
}
bool inside(Point p,Point a,Point b,Point c)
{
int val=sgn((p-a)*(b-a));
if(sgn((p-b)*(c-b))==val && sgn((p-c)*(a-c))==val)
return true;
return false;
}
Point tab[N+10];
vector<int> hull;
bool onhull[N+10];
bool vis[N+10];
bool cross_all(Point a,Point b,int n)
{
vector<Point> t[2];
for(int i=1;i<=n;i++)
{
long long tmp=(tab[i]-b)*(a-b);
if(tmp>0)
t[1].push_back(tab[i]);
else if(tmp<0)
t[0].push_back(tab[i]);
}
vector<Point> sa=t[0],sb=t[0];
sort(sa.begin(),sa.end(),[&a](Point p,Point q){ return (p-a)*(q-a)<0; });
sort(sb.begin(),sb.end(),[&b](Point p,Point q){ return (p-b)*(q-b)<0; });
for(auto v:t[1])
{
int cnt=t[0].size();
int bg=0,en=sb.size();
while(bg<en)
{
int mid=(bg+en+1)/2;
if((b-v)*(sb[mid-1]-b)>0)
bg=mid;
else
en=mid-1;
}
cnt-=bg;
bg=0,en=sa.size();
while(bg<en)
{
int mid=(bg+en+1)/2;
if((a-v)*(sa[sa.size()-mid]-a)<0)
bg=mid;
else
en=mid-1;
}
cnt-=bg;
if(cnt>0)
return true;
}
return false;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n,ans=0;
cin>>n;
for(int i=1;i<=n;i++)
cin>>tab[i].x>>tab[i].y;
sort(tab+1,tab+n+1,[](Point a,Point b){ return a.x<b.x; });
auto pop_bad=[](int x)
{
while(hull.size()>1 &&
(tab[x]-tab[hull[hull.size()-2]])*(tab[hull.back()]-tab[hull[hull.size()-2]])<0)
hull.pop_back();
hull.push_back(x);
return;
};
for(int i=1;i<=n;i++)
pop_bad(i);
for(int i=n-1;i>=1;i--)
pop_bad(i);
hull.pop_back();
for(auto v:hull)
onhull[v]=true;
//for(auto v:hull)
// cerr<<tab[v].x<<" "<<tab[v].y<<"\n";
for(int i=1;i<=n;i++)
{
if(onhull[i])
continue;
int a=1,b,c;
for(b=1,c=2;sgn((tab[hull[b]]-tab[a])*(tab[i]-tab[a]))==
sgn((tab[hull[c]]-tab[a])*(tab[i]-tab[a]));b++,c++);
b=hull[b];
c=hull[c];
for(int j=1;j<=n;j++)
{
if(j==i || j==a || j==b || j==c || !inside(tab[j],tab[a],tab[b],tab[c]))
continue;
if(inside(tab[i],tab[a],tab[b],tab[j]))
c=j;
else if(inside(tab[i],tab[a],tab[j],tab[c]))
b=j;
else if(inside(tab[i],tab[j],tab[b],tab[c]))
a=j;
}
for(int j:{a,b,c})
{
//cerr<<tab[i].x<<","<<tab[i].y<<" "<<tab[j].x<<","<<tab[j].y<<"\n";
if(!vis[j] && !cross_all(tab[i],tab[j],n))
ans++;
}
vis[i]=true;
//cerr<<tab[i].x<<" "<<tab[i].y<<" "<<ans<<"\n";
}
cout<<ans+hull.size()<<"\n";
return 0;
}
