#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<map>
using namespace std;
typedef long double ld;
typedef pair<int,int> PII;
const int MX=2020;
const ld eps=1e-9;

int N, cnt;
int read()
{
    int r=0, f=1; char ch=getchar();
    while(ch<'0'||ch>'9') {if(ch=='-') f=-1; ch=getchar();}
    while(ch>='0'&&ch<='9') {r=r*10+ch-'0'; ch=getchar();}
    return r*f;
}
ld py, px;
struct point
{
    ld x, y;
    int id;
    point operator - (const point &a)const {return {x-a.x,y-a.y,id};}
    point operator + (const point &a)const {return {x+a.x,y+a.y,id};}
    ld operator ^ (const point &a)const {return x*a.y-y*a.x;}
    bool operator < (const point &a)const
    {
        ld t1=atan2(y-py,x-px);
        ld t2=atan2(a.y-py,a.x-px);
        return t1<t2;
    }
}p[MX], np[MX], s1[MX];
map<point,int> mp;
map<PII,int> ck;
int t1, t2;
using vec=point;
struct line {point p; vec v;};
int n1(int x){return x==t1?1:x+1;}
int main()
{
    // freopen("testdata.in","r",stdin);
    N=read(); int id=1;
    for(int i=1;i<=N;i++)
    {
        scanf("%Lf%Lf",&p[i].x,&p[i].y); 
        p[i].id=i;
        if(p[i].x<p[id].x||(p[i].x==p[id].x&&p[i].y<p[id].y)) id=i;
    }   
    swap(p[1],p[id]); py=p[1].y; px=p[1].x;
    sort(p+2,p+1+N);
    s1[++t1]=p[1];
    for(int i=2;i<=N;i++)
    {
        while(t1>=2&&((s1[t1]-s1[t1-1])^(p[i]-s1[t1]))<=0) t1--;
        s1[++t1]=p[i];
    }  
    for(int i=1;i<=t1;i++) mp[s1[i]]=1;
    s1[++t1]=p[1];
    for(int i=1;i<t1;i++) ck[make_pair(s1[i].id,s1[i+1].id)]=1; 
    int ans=0;
    for(int i=1;i<=N;i++)
    {
        if(mp[p[i]]) continue;
        py=p[i].y, px=p[i].x;
        memcpy(np,p,sizeof(p));
        swap(np[i],np[1]);
        sort(np+2,np+N+1);
        np[N+1]=np[2];
        for(int j=2;j<=N;j++)
            if(ck[make_pair(np[j].id,np[j+1].id)]) ans++;
        // cout << "pi = (" << p[i].x << "," << p[i].y << "), ans=" << ans << '\n';
    }
    cout << ans+1 << '\n';
    return (0-0);
}