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

int n,ans,v[2100],st[2100],tp;
struct point {
    LL x,y; int id;
    double ang;
    point operator-(const point& p) const {
        return (point){x-p.x,y-p.y,0,0};
    }
}p[2100],pp[2100];

LL dis(point p1,point p2) {
    return (p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y);
}

bool cmp(point x,point y)
{
    if(x.ang==y.ang) return dis(x,p[1])<dis(y,p[1]);
    return x.ang<y.ang;
}

LL cross(point x,point y) {
    return x.x*y.y-x.y*y.x;
}

int main()
{
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    cin>>n;
    for(int i=1;i<=n;i++) cin>>p[i].x>>p[i].y;
    for(int i=2;i<=n;i++) {
        if(p[i].y<p[1].y||(p[i].y==p[1].y&&p[i].x<p[1].x)) swap(p[1],p[i]);
    }
    for(int i=2;i<=n;i++) {
        p[i].ang=atan2(p[i].y-p[1].y,p[i].x-p[1].x);
    }
    sort(p+2,p+n+1,cmp);
    for(int i=1;i<=n;i++) p[i].id=i;
    st[++tp]=1;
    for(int i=2;i<=n;i++) {
        while(tp>=2&&cross(p[st[tp]]-p[st[tp-1]],p[i]-p[st[tp]])<0) --tp;
        st[++tp]=i;
    }
    for(int i=1;i<=tp;i++) v[st[i]]=1;
    for(int i=1;i<=n;i++) pp[i]=p[i];
    for(int i=1;i<=n;i++) {
        if(v[i]) continue;
        for(int j=1;j<=n;j++) p[j]=pp[j];
        swap(p[1],p[i]);
        for(int j=2;j<=n;j++) p[j].ang=atan2(p[j].y-p[1].y,p[j].x-p[1].x);
        sort(p+2,p+n+1,cmp);
        int sta=2;
        while(!v[p[sta].id]) ++sta;
        for(int j=2;j<n;j++) {
            int nxt=j+1;
            while(nxt<n&&p[nxt+1].ang==p[j+1].ang&&!v[p[nxt].id]) ++nxt;
            if(v[p[j].id]&&v[p[nxt].id]) ++ans;
            j=nxt-1;
        }
        if(v[p[n].id]&&v[p[sta].id]) ++ans;
    }
    cout<<ans+1<<endl;
    return 0;
}