#include <bits/stdc++.h>

using namespace std;
#define int long long
const double eps=1e-9;
const double pi=acos(-1.0);
const int maxn=1e4+10;

int sgn(double x)
{
	if (fabs(x)<eps) return 0;
	if (x<0) return -1;
	return 1;
}

struct point{
	double x;
	double y;
	int vis;
	point(){}
	point (double a,double b){
		x=a;
		y=b;
		vis=0;
	}
	point operator - (point b){
		return point(x-b.x,y-b.y);
	}
	point operator + (point b){
		return point(x+b.x,y+b.y);
	}
	double operator ^ (point b){
		return x*b.y-y*b.x;
	}
	double operator * (point b){
		return x*b.x+y*b.y;
	}
	point operator * (double b){
		return point(x*b,y*b);
	}
	point operator / (double b){
		return point(x/b,y/b);
	}
	static double cross(point a,point b){
		return a.x*b.y-a.y*b.x;
	}
	static double dot(point a,point b){
		return a.x*b.x+a.y*b.y;
	}
	point rotleft(){			//逆时针转90 
		return point(-y,x);
	}
	point rotright(){			//顺时针转90 
		return point(y,-x);
	}
	point rotate(point p,double angle){
		point v=(*this)-p;
		double c=cos(angle);
		double s=sin(angle);
		return point(p.x+v.x*c-v.y*s,p.y+v.x*s+v.y*c);
	}
	static double dis2(point a,point b){
		return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);
	}
	double dis(point b){
		return sqrt((x-b.x)*(x-b.x)+(y-b.y)*(y-b.y));
	}
};

struct line{
	//a->b
	point a;
	point b;
	line(){}
	line(point q,point w){					//两点式 
		a=q;
		b=w;
	}
	line(point p,double angle){				//斜率式 
		a=p;
		if (sgn(angle-pi/2)==0) b=(a+point(0,1));
		else b=(a+point(1,tan(angle)));
	}
	line(double A,double B,double C){		//Ax+By+C=0 
		if (sgn(A)==0){
			a=point(0.0,-C/B);
			b=point(1.0,-C/B);
		}
		else if (sgn(B)==0){
			a=point(-C/A,0);
			b=point(-C/A,1);
		}
		else{
			a=point(0,-C/B);
			b=point(1,(-A-C)/B);
		}
	}
	point crosspoint(line l){				//找交点 
		double a1=point::cross(l.b-a,b-a);
		double a2=point::cross(l.a-a,b-a);
		return point((a1*l.a.x-a2*l.b.x)/(a1-a2),(a1*l.a.y-a2*l.b.y)/(a1-a2));
	}
	double pointtoLine(point p){				//点到直线距离 
		return fabs((p-a)^(b-a))/sqrt(point::dis2(a,b));
	}
	double pointtoSeg(point p){					//点到线段距离 
		if (sgn((p-a)*(b-a))<0 || sgn((p-b)*(a-b))<0) return min(point::dis2(p,a),point::dis2(p,b));
		return pointtoLine(p);
	}
	point lineprog(point p){					//点在直线上投影 
		return a+(((b-a)*((b-a)*(p-a)))/(point::dis2(b,a)));
	}
	point mirrorpoint(point p){					//点关于直线对称点 
		point q=lineprog(p);
		return point(2*q.x-p.x,2*q.y-p.y);
	}
};

struct circle{
	point p;
	double r;
	circle(){}
	circle(point a,double b){
		p=a;
		r=b;
	}
	circle(double x,double y,double a){
		p=point(x,y);
		r=a;
	}
	circle(point a,point b,point c){				//三角形外接圆 
		line u=line((a+b)/2,((a+b)/2)+((b-a).rotleft()));
		line v=line((b+c)/2,((b+c)/2)+((c-b).rotleft()));
		p=u.crosspoint(v);
		r=sqrt(point::dis2(p,a));
	}
	circle(point a,point b,point c,bool inside){			//三角形内切圆,inside没有用,只是用来区分两个构造函数  
		double m=atan2((b-a).y,(b-a).x);
		double n=atan2((c-a).y,(c-a).x);
		if (inside) r=0; 
		line u,v;
		u.a=a;
		u.b=u.a+point(cos((n+m)/2),sin((n+m)/2));
		v.a=b;
		m=atan2((a-b).y,(a-b).x);
		n=atan2((c-b).y,(c-b).x);
		v.b=v.a+point(cos((n+m)/2),sin((n+m)/2));
		p=u.crosspoint(v);
		r=line(a,b).pointtoSeg(p);
	} 
};

struct MRCLP{								//最小矩形覆盖信息 
	line lne;
	point upp;
	point lep;
	point rip;
	MRCLP(){}
	MRCLP(line a,point u,point l,point r){
		lne=a;
		upp=u;
		lep=l;
		rip=r;
	}
	point findcp(point b,point inline1,point inline2,point sf){
		return b-inline1*(point::cross(inline2,sf)/point::cross(inline1,inline2));
	}
	point equer(point a)
	{
		return point(a.y,-a.x);
	}
	void getcrosspoint(){
		vector<point> ans(10);
		point le=lne.b-lne.a;
		point anot=equer(le);
		ans[0]=MRCLP::findcp(lne.b,le,anot,rip-lne.b);
		ans[1]=MRCLP::findcp(rip,anot,le,upp-rip);
		ans[2]=MRCLP::findcp(upp,le,anot,lep-upp);
		ans[3]=MRCLP::findcp(lep,anot,le,lne.b-lep);
		int ori=0;
		for (int i=0;i<=3;i++){
			if (sgn(ans[i].x)==0) ans[i].x=0.000;
			if (sgn(ans[i].y)==0) ans[i].y=0.000;
		}
		for (int i=1;i<=3;i++){
			if (ans[i].y<ans[ori].y||(ans[i].y==ans[ori].y&&ans[i].x<ans[ori].x)) ori=i;
		}
		swap(ans[0],ans[ori]);
		for (int i=1;i<=3;i++){
			for (int j=1;j<=3;j++){
				if (point::cross(ans[i]-ans[0],ans[j]-ans[i])>0) swap(ans[i],ans[j]);
			}
		}
		for (int i=0;i<=3;i++){
			printf ("%.5lf %.5lf\n",ans[i].x,ans[i].y);
		}
	}
};

struct polygon{								//多边形 
	vector<point> in;						//输入的点集，求凸包操作后成为凸包上的点集(逆时针方向) 
	vector<point> rein;
	int cnt;
	MRCLP tmp;
	polygon(){}
	polygon(vector<point> a){
		in=a;
	}
	bool isPolygon(){
		return in.size()>=3;
	}
	void quicksort(int l, int r)				//快排 
	{
		if (l<r) {
			swap(in[l],in[(l+r)/2]);
			int i=l,j=r;
			point x=in[l];
			while (i<j) {
				while (i<j&&(point::cross(in[j]-in[0],x-in[j])<0 ||
				 	(point::cross(in[j]-in[0],x-in[j])==0&&point::dis2(in[j],in[0])>point::dis2(x,in[0])))) j--;
				if (i<j) in[i++]=in[j];
				while (i<j&&(point::cross(in[i]-in[0],x-in[i])>0 ||
				 	(point::cross(in[i]-in[0],x-in[i])==0&&point::dis2(in[i],in[0])<point::dis2(x,in[0])))) i++;
				if (i<j) in[j--]=in[i];
			}
			in[i]=x;
			quicksort(l,i-1);
			quicksort(i+1,r);
		}
	}
	void convexHell(){							//查找凸包上的点 
		rein=in;
		int ori=0;
		for (int i=0;i<in.size();i++){
			if (in[i].y<in[ori].y||(in[i].y==in[ori].y&&in[i].x<in[ori].x)) ori=i;
		}
		swap(in[0],in[ori]);
		quicksort(1,in.size()-1);
		vector<point> tmp(in.size()+10);
		int nw=-1;
		for (int i=0;i<in.size();i++){
			while (nw>=1){
				if (point::cross(tmp[nw]-tmp[nw-1],in[i]-tmp[nw])>0) break;
				else if (point::cross(tmp[nw]-tmp[nw-1],in[i]-tmp[nw])==0){
					nw--;
					break;
				}
				else nw--;
			}
			tmp[++nw]=in[i];
		}
		in.clear();
		for (int i=0;i<=nw;i++) in.push_back(tmp[i]);
	}
	double diameter(){						//旋转卡壳(返回直径的平方) 
		double ans=0;
		int nw=1;
		for (int i=1;i<=in.size();i++){
			while ( point::cross(in[i%in.size()]-in[i-1],in[nw%in.size()]-in[i%in.size()])<
				point::cross(in[i%in.size()]-in[i-1],in[(nw+1)%in.size()]-in[i%in.size()]) ) nw++;
			ans=max({ans,point::dis2(in[nw%in.size()],in[i%in.size()]),point::dis2(in[nw%in.size()],in[i-1])});
		}
		return ans;
	}
	double MRC(){							//最小矩形覆盖  
		double ans=1e18;
		int upp=1,lep=in.size()-1,rip=1;
		while (lep>=1&&point::dot(in[0]-in[1],in[lep]-in[1])<=point::dot(in[0]-in[1],in[lep-1]-in[1])) lep--;			//左侧顶点先反向遍历，不然会WA 
		for (int i=1;i<=in.size();i++){
			while ( point::cross(in[i%in.size()]-in[i-1],in[upp%in.size()]-in[i%in.size()])<=
				point::cross(in[i%in.size()]-in[i-1],in[(upp+1)%in.size()]-in[i%in.size()]) ) upp++;
			while (point::dot(in[i%in.size()]-in[i-1],in[rip%in.size()]-in[i-1])<=point::dot(in[i%in.size()]-in[i-1],in[(rip+1)%in.size()]-in[i-1])) rip++;
			while ( point::dot(in[i-1]-in[i%in.size()],in[lep%in.size()]-in[i%in.size()])<=
				point::dot(in[i-1]-in[i%in.size()],in[(lep+1)%in.size()]-in[i%in.size()]) ) lep++;
			double area=fabs(point::cross(in[i%in.size()]-in[i-1],in[upp%in.size()]-in[i%in.size()]));
			double lefleg=fabs(point::dot(in[i-1]-in[i%in.size()],in[lep%in.size()]-in[i%in.size()]));
			double rigleg=fabs(point::dot(in[i%in.size()]-in[i-1],in[rip%in.size()]-in[i-1]));
			double dezleg=fabs(point::dot(in[i%in.size()]-in[i-1],in[i-1]-in[i%in.size()]));
			double S=area*(lefleg+rigleg-dezleg)/dezleg;
			if (sgn(S-ans)==-1){
				tmp=MRCLP(line(in[i%in.size()],in[i-1]),in[upp%in.size()],in[lep%in.size()],in[rip%in.size()]);
				ans=S;
			}
		}
		return ans;
	}
	double cularea(){						//计算面积 
		if (!isPolygon()) return -1.0;
		double ans=0;
		for (int i=0;i<in.size();i++){
			ans+=point::cross(in[i],in[(i+1)%in.size()]);
		}
		return ans/2;
	}
	double culcel(){						//计算周长 
		if (!isPolygon()) return -1.0;			//洛谷模板题上删去这句，答案有非多边形情况 
		double ans=0;
		for (int i=0;i<in.size();i++){
			ans+=sqrt(point::dis2(in[i],in[(i+1)%in.size()]));
		}
		return ans;
	}
};

struct HPIL:public line{			//半平面交直线特性 
	double angle;
	HPIL(){}
	HPIL(point q,point w){
		a=q;
		b=w;
		angle=atan2((b-a).y,(b-a).x);
	}
	HPIL(line z){
		a=z.a;
		b=z.b;
		angle=atan2((b-a).y,(b-a).x);
	}
	bool operator < (HPIL t){
		if (sgn(angle-t.angle)==0) return sgn(point::cross(t.a-a,t.b-a))==1;
		return sgn(angle-t.angle)==-1;
	}
};

struct HPI{								//半平面交 
	vector<HPIL> in;
	HPIL e[maxn];
	HPIL dq[maxn];
	int cnt=1,top,back;
	HPI(){}
	HPI(vector<HPIL> a){
		in=a;
	}
	void unique(){						//去重 
		cnt=0;
		for (int i=1;i<(int)in.size();i++){
			if (sgn(in[i].angle-in[i-1].angle)!=0) in[++cnt]=in[i];
		}
		for (int i=0;i<=cnt;i++) e[i+1]=in[i];
		cnt++;
	}
	bool cp(HPIL a,HPIL b,HPIL c){
		point o=b.crosspoint(c);
		return sgn(point::cross(a.a-o,a.b-o))==-1;
	}
	void toans(){						//求解 
		sort(&in[0],&in[in.size()]);
		unique();
		top=2,back=1;
		dq[1]=e[1];
		dq[2]=e[2];
		for (int i=3;i<=cnt;i++){
			while (back<top&&cp(e[i],dq[top],dq[top-1])) top--;
			while (back<top&&cp(e[i],dq[back],dq[back+1])) back++;
			dq[++top]=e[i];
		}
		while (back<top&&cp(dq[back],dq[top],dq[top-1])) top--;
		while (back<top&&cp(dq[top],dq[back],dq[back+1])) back++;
	}
	vector<point> getpolygon(){
		vector<point> ans;
		for (int i=back;i<top;i++) ans.push_back(dq[i].crosspoint(dq[i+1]));
		if (top-back>1) ans.push_back(dq[top].crosspoint(dq[back]));
		return ans;
	}
};

signed main()
{
	int n;
	cin>>n;
	vector <point> a;
	for (int i=1;i<=n;i++){
		int x,y;
		cin>>x>>y;
		a.push_back(point(x,y));
	}
	polygon pl=polygon(a);
	pl.convexHell();
	for (auto p:pl.in){
		for (int i=0;i<n;i++){
			if (!sgn(p.x-pl.rein[i].x)&&!sgn(p.y-pl.rein[i].y)){
				pl.rein[i].vis=1;
				break;
			}
		}
	}
	int ans=1;
	for (int i=0;i<n;i++){
		if (pl.rein[i].vis) continue;
		vector <pair<double,int> > as;
		int cnt=0;
		for (int j=0;j<n;j++){
			if (i==j) continue;
			as.push_back({atan2((pl.rein[j]-pl.rein[i]).y,(pl.rein[j]-pl.rein[i]).x),pl.rein[j].vis});
			cnt++;
		}
		sort(&as[0],&as[cnt]);
		for (int j=0;j<cnt;j++){
			if (as[j].second&&as[(j+1)%cnt].second) ans++;
		}
	}
	cout<<ans<<'\n';
}