#include<iostream>
#include<vector>
#include<algorithm>
#include<cstring>
using namespace std;
struct point
{
	int x,y;
};
inline bool operator <(const point &a,const point &b)
{
	return a.x==b.x?a.y<b.y:a.x<b.x;
}
inline point operator -(const point &a,const point &b)
{
	return {a.x-b.x,a.y-b.y};
}
inline long long operator *(const point &a,const point &b)
{
	return (long long)a.x*b.y-(long long)a.y*b.x;
}
int n,head,sta[2010],num,p[2010];
point a[2010],A;
bool mark[2010],Mark[2010];
vector<int> v;
inline bool cmp(int x,int y)
{
	point p=a[x]-A,q=a[y]-A;
	return ((p.x<0)==(q.x<0))?p*q>0:p.x<0;
}
inline bool in(int x,int y,int z)
{
	bool t=(a[p[x]]-A)*(a[z]-A)>0;
	return t==((A-a[p[y]])*(a[z]-a[p[y]])>0)
	&&t==((a[p[y]]-a[p[x]])*(a[z]-a[p[x]])>0);
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i].x>>a[i].y;
	}
	sort(a+1,a+n+1),sta[head=1]=1;
	for(int i=2;i<=n;i++)
	{
		while(head>1&&(a[sta[head]]-a[sta[head-1]])
		*(a[i]-a[sta[head-1]])>0)
		{
			head--;
		}
		sta[++head]=i;
	}
	num=head,memcpy(p,sta,sizeof(p));
	sta[head=1]=n;
	for(int i=n-1;i;i--)
	{
		while(head>1&&(a[sta[head]]-a[sta[head-1]])
		*(a[i]-a[sta[head-1]])>0)
		{
			head--;
		}
		sta[++head]=i;
	}
	for(int i=2;i<=head;i++)
	{
		p[++num]=sta[i];
	}
	for(int i=1;i<=num;i++)
	{
		mark[p[i]]=1;
	}
	int ans=1;
	for(int i=1;i<=n;i++)
	{
		if(mark[i])
		{
			continue;
		}
		A=a[i],v.clear();
		for(int j=1;j<=n;j++)
		{
			if(i!=j&&!mark[j])
			{
				v.emplace_back(j);
			}
		}
		sort(v.begin(),v.end(),cmp);
		memset(Mark,0,sizeof(Mark));
		for(int j=0,k=1;j<v.size();j++)
		{
			while(!in(k,k+1,v[j]))
			{
				k=k+1<num?k+1:1;
			}
			Mark[k]=1;
		}
		for(int j=1;j<num;j++)
		{
			ans+=!Mark[j];
		}
	}
	cout<<ans<<endl;
	return 0;
}