#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define MP make_pair
mt19937 rnd(time(0));
const int MAXN=2e3+5;
struct node{ld x,y;bool inc;}a[MAXN],b[MAXN];
ld d[MAXN];int id[MAXN];
node operator -(node x,node y){return (node){x.x-y.x,x.y-y.y,x.inc};}
ld operator *(node x,node y){return x.x*y.y-x.y*y.x;}
bool operator <(node x,node y){return (x.x!=y.x?x.x<y.x:x.y<y.y);}
ld dis(node x){return sqrt(x.x*x.x+x.y*x.y);} 
ld deg(node x){return atan2(x.x,x.y);} 
node st[MAXN];int top=0;
int n;
int main(){
	ios::sync_with_stdio(false);
	// freopen("Otomachi_Una.in","r",stdin);
	// freopen("Otomachi_Una.out","w",stdout);
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i].x>>a[i].y;
		if(i>1&&(a[i].y<a[1].y||a[i].y==a[1].y&&a[i].x<a[1].x)) swap(a[1],a[i]);
	}
	sort(a+2,a+n+1,[](node x,node y){
		ld tmp=(x-a[1])*(y-a[1]);
		return tmp>0||tmp==0&&dis(x-a[1])<dis(y-a[1]); 
	});
	st[top=1]=a[1];
	for(int i=2;i<=n;i++){
		while(top>1&&(a[i]-st[top])*(a[i]-st[top-1])>0) top--;
		st[++top]=a[i];
	}
	set<node> se;
	for(int i=1;i<=top;i++) se.insert(st[i]);
	for(int i=1;i<=n;i++) a[i].inc=se.count(a[i]);
	int ans=1;
	for(int i=1;i<=n;i++) if(!a[i].inc){
		// cout<<"Cal "<<a[i].x<<' '<<a[i].y<<' '<<ans<<'\n';
		int m=0;
		for(int j=1;j<=n;j++) if(i!=j){
			b[++m]=a[j]-a[i],d[m]=deg(b[m]),id[m]=m;
		}
		sort(id+1,id+m+1,[&](int x,int y){
			return d[x]<d[y];
		});
		id[n]=id[1];
		for(int i=1;i<n;i++) if(b[id[i]].inc&&b[id[i+1]].inc) ans++; 
	}
	cout<<ans<<'\n';
	return 0;
}