#include <bits/stdc++.h>
#define inf 1000000007
#define mod 1000000007
// #define int long long
// #pragma GCC optimize("Ofast","inline","-ffast-math")
// #pragma GCC target("avx,sse2,sse3,sse4,mmx")
using namespace std;
template <typename T> void read(T &x){
	x=0;char ch=getchar();int fh=1;
	while (ch<'0'||ch>'9'){if (ch=='-')fh=-1;ch=getchar();}
	while (ch>='0'&&ch<='9')x=x*10+ch-'0',ch=getchar();
	x*=fh;
}
template <typename T> void write(T x) {
	if (x<0) x=-x,putchar('-');
	if (x>9) write(x/10);
	putchar(x%10+'0');
}
template <typename T> void writeln(T x) {
	write(x);
	puts("");
}
const double pi=acos(0)*2,eps=1e-6;
int n,stk[2005],tt,ans=1;
bool ins[2005];
struct point
{
	int x,y;
	bool operator<(const point &o) const{return (x==o.x?y<o.y:x<o.x);}
	point operator-(const point &o) const{return {x-o.x,y-o.y};}
	long long operator*(const point &o) const{return 1ll*x*o.y-1ll*y*o.x;}
}p[2005];
pair<int,int> val[2005];
signed main()
{
	// freopen(".in","r",stdin);
	// freopen(".out","w",stdout);
	read(n);
	for(int i=1;i<=n;++i)
	{
		read(p[i].x);
		read(p[i].y);
	}
	sort(p+1,p+n+1);
	stk[tt=1]=1;
	for(int i=2;i<=n;++i)
	{
		while(tt>1&&(p[stk[tt]]-p[stk[tt-1]])*(p[i]-p[stk[tt]])<=0) ins[stk[tt--]]=0;
		ins[stk[++tt]=i]=1;
	}
	for(int i=n-1,j=tt;i>=1;--i)
	{
		if(ins[i]) continue;
		while(tt>j&&(p[stk[tt]]-p[stk[tt-1]])*(p[i]-p[stk[tt]])<=0) ins[stk[tt--]]=0;
		ins[stk[++tt]=i]=1;
	}
	stk[tt]=stk[1];
	for(int i=1;i<tt;++i)
	{
		vector<int> id;
		for(int j=1;j<=n;++j)
			if(!ins[j]) id.push_back(j);
		sort(id.begin(),id.end(),[i](int a,int b){
			double ang1=atan2(p[a].y-p[stk[i]].y,p[a].x-p[stk[i]].x)-atan2(p[stk[i+1]].y-p[stk[i]].y,p[stk[i+1]].x-p[stk[i]].x);
			double ang2=atan2(p[b].y-p[stk[i]].y,p[b].x-p[stk[i]].x)-atan2(p[stk[i+1]].y-p[stk[i]].y,p[stk[i+1]].x-p[stk[i]].x);
			if(ang1<-pi-eps) ang1+=pi*2;
			if(ang1>pi+eps) ang1-=pi*2;
			if(ang2<-pi-eps) ang2+=pi*2;
			if(ang2>pi+eps) ang2-=pi*2;
			ang1=fabs(ang1);ang2=fabs(ang2);
			return ang1<ang2;
		});
		for(int j=0;j<id.size();++j)
			val[id[j]].first=j;
		sort(id.begin(),id.end(),[i](int a,int b){
			double ang1=atan2(p[a].y-p[stk[i+1]].y,p[a].x-p[stk[i+1]].x)-atan2(p[stk[i]].y-p[stk[i+1]].y,p[stk[i]].x-p[stk[i+1]].x);
			double ang2=atan2(p[b].y-p[stk[i+1]].y,p[b].x-p[stk[i+1]].x)-atan2(p[stk[i]].y-p[stk[i+1]].y,p[stk[i]].x-p[stk[i+1]].x);
			if(ang1<-pi-eps) ang1+=pi*2;
			if(ang1>pi+eps) ang1-=pi*2;
			if(ang2<-pi-eps) ang2+=pi*2;
			if(ang2>pi+eps) ang2-=pi*2;
			ang1=fabs(ang1);ang2=fabs(ang2);
			return ang1<ang2;
		});
		for(int j=0;j<id.size();++j)
			val[id[j]].second=j;
		sort(id.begin(),id.end(),[](int a,int b){
			return val[a]<val[b];
		});
		int mn=inf;
		for(int i:id)
		{
			if(val[i].second<mn) ++ans;
			mn=min(mn,val[i].second);
		}
	}
	writeln(ans);
	return 0;
}