// what is matter? never mind. 
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,sse4,popcnt,abm,mmx,avx,avx2")
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
#define ull unsigned long long
//#define int long long
#define SZ(x) ((int)((x).size()))
#define ALL(x) (x).begin(),(x).end()
using namespace std;
inline int read()
{
	char c=getchar();int x=0;bool f=0;
	for(;!isdigit(c);c=getchar())f^=!(c^45);
	for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
	return f?-x:x;
}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

typedef double db;
const db eps=1e-8,pi=3.14159265358979323846;
int sgn(int x){return x<0?-1:x>0;}
int cmp(int a,int b){return sgn(a-b);}

struct P{
	int x,y,id;
	P(int x=0,int y=0):x(x),y(y){}
	P&operator +=(P o){return x+=o.x,y+=o.y,*this;}
	P&operator -=(P o){return x-=o.x,y-=o.y,*this;}
	P&operator *=(int o){return x*=o,y*=o,*this;}
	P&operator /=(int o){return x/=o,y/=o,*this;}
	friend P operator +(P a,P b){return a+=b;}
	friend P operator -(P a,P b){return a-=b;}
	friend P operator *(P a,int b){return a*=b;}
	friend P operator /(P a,int b){return a/=b;}
	friend bool operator <(P a,P b){return fabs(a.x-b.x)<eps?a.y<b.y:a.x<b.x;}
	friend bool operator ==(P a,P b){return cmp(a.x,b.x)==0 && cmp(a.y,b.y)==0;}
	friend bool operator !=(P a,P b){return !(a==b);}
	friend int operator %(P a,P b){return a.x*b.x+a.y*b.y;} // dot
	friend int operator *(P a,P b){return a.x*b.y-a.y*b.x;} // cross
	
	P rot90(){return P(-y,x);}
	db ang(){return atan2(y,x);}
	db len(){return sqrt(x*x+y*y);}
	int len2(){return x*x+y*y;}
	
	int half(){return sgn(y)==1||(sgn(y)==0&&sgn(x)>=0);}
//	P unit(){return ((*this))/len();}
	
	void read(){cin>>x>>y;}
	void out(){cout<<"("<<x<<","<<y<<")"<<endl;}
};
bool cmp_dir(P a,P b){
	if(a.half()!=b.half())return a.half()<b.half();
	return sgn(a*b)>0;
}

db dis(P a,P b){return (a-b).len();}
int cross(P a,P b,P c){
	// (a->b)*(a->c)
	return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
int cmp3(P a,P b,P c){
	return sgn(cross(a,b,c));
}

vector<P>convex(vector<P>a){
	int n=a.size(),m=0; if(n<=1)return a;
	sort(a.begin(),a.end());
	vector<P>st(n*2); int tp=0;
	For(i,0,n-1){
		while(tp>1 && cmp3(st[tp-2],st[tp-1],a[i])<=0)--tp;
		st[tp++]=a[i];
	}
	int t=tp;
	Rep(i,n-2,0){
		while(tp>t && cmp3(st[tp-2],st[tp-1],a[i])<=0)--tp;
		st[tp++]=a[i];
	}
	st.resize(tp-1);
	return st;
}

#define maxn 200005
#define inf 0x3f3f3f3f

int n;
P a[maxn];
bool vis[maxn];
int res;
set<int>mp[maxn];

signed main()
{
	n=read();
	For(i,1,n){
		a[i].read();
		a[i].id=i;
	}
	vector<P>p(n);
	For(i,0,n-1)p[i]=a[i+1];
	p=convex(p);
	For(i,0,SZ(p)-1){
		int u=p[i].id,v=p[(i+1)%SZ(p)].id;
		mp[u].insert(v),mp[v].insert(u);
	}
	for(auto t:p) vis[t.id]=1;
	res=1;
	For(i,1,n) if(!vis[i]) {
		vector<P>b;
		For(j,1,n) if(j!=i) {
			P tmp=a[j]-a[i];
			tmp.id=j;
			b.pb(tmp);
		}
		sort(b.begin(),b.end(),cmp_dir);
		For(i,0,SZ(b)-1){
			int u=b[i].id,v=b[(i+1)%SZ(b)].id;
			if(mp[u].count(v)) ++res;
		}
	}
	cout<<res;
	return 0;
}

/*

*/