#include <bits/stdc++.h>
using namespace std;

#define int long long

#define fs first
#define sc second

struct point {
	int x,y;
};



bool cmp(point p1,point p2) {
	if(p1.x!=p2.x) return p1.x<p2.x;
	return p1.y<p2.y;
}

__int128 cross(int xi,int yi,int xj,int yj) { //计算叉积
	return ((__int128)xi*yj-(__int128)xj*yi);
}

__int128 compare(point a,point b,point c) { //计算极角
	return cross((b.x-a.x),(b.y-a.y),(c.x-a.x),(c.y-a.y));
}

point c;

bool cmp1(point a,point b) {
	if(compare(c,a,b)==0) return a.x < b.x;
	return compare(c,a,b) < 0;
}

bool cmp2(pair<point,int>p1,pair<point,int>p2){
	return cmp1(p1.fs,p2.fs);
}

int check(point a1,point a2,point b)
{
	int x1 = a2.x-a1.x,y1 = a2.y-a1.y;
	int x2 = b.x-a1.x,y2 = b.y-a1.y;
	return cross(x1,y1,x2,y2)>0;
}

int g[2005][2005];

signed main() {
	int n;
	cin>>n;
	vector<point>ar(n);
	for(int i=0; i<n; i++) {
		cin>>ar[i].x>>ar[i].y;
	}
	sort(ar.begin(),ar.end(),cmp);

	int m = 0;
	vector<int>st(n);
	vector<pair<point,int>>br;
	for(int i=0;i<n;i++){
		while(br.size()>=2 && check(br[br.size()-2].fs,br[br.size()-1].fs,ar[i])){
			pair<point,int> t = br.back();
			st[t.sc] = 0;
			br.pop_back();	
		}
		st[i] = 1;
		br.push_back({ar[i],i});
	}
	m = br.size();
	st[0] = 0;
	for(int i=n-1;i>=0;i--){
		if(st[i]) continue;
		while(br.size()>=2 && check(br[br.size()-2].fs,br[br.size()-1].fs,ar[i])){
			pair<point,int> t = br.back(); 
			st[t.sc] = 0;
			br.pop_back();	
		}
		st[i] = 1;
		br.push_back({ar[i],i});
	}
	
	m = br.size();
	for(int i=0;i<m;i++){
		int id1 = br[i].sc,id2 = br[(i+1)%m].sc;
		if(id1 != id2) g[id1][id2] = g[id2][id1] = 1;
	}
	
	int ans = 1;
	for(int i=0;i<n;i++){
		if(st[i]) continue;
		vector<pair<point,int>>dr;
		for(int j=0;j<n;j++){
			if(i==j) continue;
			dr.push_back({ar[j],j});
		}
		c = ar[i];
		sort(dr.begin(),dr.end(),cmp2);
		
		for(int j=0;j<n-1;j++){
			int id1 = dr[j].sc,id2 = dr[(j+1)%(n-1)].sc;
			ans += g[id1][id2];
		}
  	}		
	cout<<ans;
}