#include<bits/stdc++.h>
using namespace std;
#define int long long
#define db double
const int mod=1e9+7;
const int N=2e3+10;
const db PI=acos(-1);
const db eps=1e-14;
int n,tp,s[N],whe[N],T,vis[N],ans,m,now,st[N];
struct V
{
    db x,y;
    int id;
}a[N],b[N];
db calcompare(db x,db y,db xx,db yy)
{
    return x*yy-xx*y;
}
bool cmp(V a,V b)
{
    if(a.x==b.x) return a.y<b.y;
    return a.x<b.x;
}
bool cmp2(V A,V B)
{
    V c;
    c=a[now];
    if(calcompare(A.x-c.x,A.y-c.y,B.x-c.x,B.y-c.y)==0)
        return A.x<B.x;
    else return calcompare(A.x-c.x,A.y-c.y,B.x-c.x,B.y-c.y)>0;
}
void solve()
{
    m=0;
    for(int i=1;i<=n;i++) 
    {
        if(i==now) continue;
        b[++m]=a[i];b[m].id=i;
    }
    sort(b+1,b+1+m,cmp2);
    for(int i=1;i<=m;i++)
    {
        st[b[i].id]=i;
    }
    for(int i=1;i<tp;i++)
    {
        if(abs(st[s[i]]-st[s[i+1]])==1||abs(st[s[i]]-st[s[i+1]])==m-1) 
        ans++;
    }
}
signed main()
{
    std::ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i].x>>a[i].y;
    sort(a+1,a+n+1,cmp);
    s[++tp]=1;
    for(int i=2;i<=n;i++)
    {
        while(tp>=2&&calcompare(a[s[tp]].x-a[s[tp-1]].x,a[s[tp]].y-a[s[tp-1]].y,a[i].x-a[s[tp]].x,a[i].y-a[s[tp]].y)<=0)
        {
            tp--;
            whe[s[tp+1]]=0;
        }
        s[++tp]=i;
        whe[i]=1;
    }
    int sum1=tp;
    for(int i=n-1;i>=1;i--)
    {
        if(!whe[i])
        {
            while(tp>sum1&&calcompare(a[s[tp]].x-a[s[tp-1]].x,a[s[tp]].y-a[s[tp-1]].y,a[i].x-a[s[tp]].x,a[i].y-a[s[tp]].y)<=0)
            {
                tp--;
                whe[s[tp+1]]=0;
            }
            s[++tp]=i;
            whe[i]=1;
        }
    }
    for(int i=1;i<=tp;i++)
    {
        vis[s[i]]=1;
        //cout<<s[i]<<"asdasd"<<endl;
    }
    for(int i=1;i<=n;i++)
    {
        if(!vis[i]) now=i,solve();
    }
    cout<<ans+1;
    return 0;
}