#include<bits/stdc++.h>
using namespace std;
#define x first
#define y second
const double eps=1e-8;
typedef pair<double ,double >pdd;
int stk[2010],top;
int n;
pdd p[2010];

pdd operator-(pdd a,pdd b){
    return {a.x-b.x,a.y-b.y};
}
double cross(pdd a,pdd b){
    return a.x*b.y-a.y*b.x;
}
double area(pdd a,pdd b,pdd c){
    return cross(b-a,c-a);
}
bool use[2010];
void andrew(){
    sort(p+1,p+n+1);
    for(int i=1;i<=n;i++){
        while(top>=2&&area(p[stk[top-1]],p[stk[top]],p[i])>=0)use[stk[top]]=0,top--;
        stk[++top]=i;
        use[i]=1;
    }
    use[1]=0;
    
    for(int i=n;i>=1;i--){
        if(use[i])continue;
        while(top>=2&&area(p[stk[top-1]],p[stk[top]],p[i])>=0)top--;
        stk[++top]=i;
        use[i]=1;
    }
    for(int i=1;i<=top;i++)use[stk[i]]=0;
}
pdd c[2010];
double angle(pdd a){
    double ans=atan2(a.y,a.x);
    // if(ans<0)ans+=2*acos(-1);
    return ans;
}
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>p[i].x>>p[i].y;
    }
    andrew();
    // for(int i=1;i<=top;i++)cout<<p[stk[i]].x<<" "<<p[stk[i]].y<<endl;
    int ans=1;
    // for(int i=1;i<=n;i++)cout<<use[i]<<endl;
    for(int i=2;i<=top;i++){
        int cnt=0;
        for(int j=1;j<=n;j++){
            if(!use[j])continue;
            double x1=angle(p[stk[i]]-p[stk[i-1]])-angle(p[j]-p[stk[i-1]]);
            double x2=angle(p[j]-p[stk[i]])-angle(p[stk[i-1]]-p[stk[i]]);
            if(x1<0)x1+=acos(-1);
            if(x2<0)x2+=acos(-1);
            c[++cnt]={x1,x2};
        }
        
        double minn=1e9;
        sort(c+1,c+cnt+1);
        for(int i=1;i<=cnt;i++){
            // cout<<c[i].x<<" "<<c[i].y<<endl;
            if(minn<c[i].second);
            else ans++;
            minn=min(minn,c[i].second);
           
        } 
        // cout<<ans<<endl;
    }
    cout<<ans;
}