#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

const int N=120005;
int n, k;

struct coord
{
    double x, y;
};
coord v[N], d[N];

bool mic(coord a, coord b)
{
    if (a.x<b.x) return 1;
    else
    {
        if (a.x==b.x && a.y<b.y) return 1;
        return 0;
    }
}

double ordine(coord a, coord b, coord c)
{
    return (a.x-c.x)*(b.y-c.y)-(a.y-c.y)*(b.x-c.x);
}

int main()
{
    int i;
    f>>n;
    for (i=1; i<=n; i++) f>>v[i].x>>v[i].y;

    sort(v+1, v+n+1, mic);

    //for (i=1; i<=n; i++) cout<<fixed<<setprecision(6)<<v[i].x<<" "<<v[i].y<<"\n";

    for(i=1; i<=n; i++)
    {
        while (k>=2 && ordine(d[k-1], d[k], v[i])<=0) k--;
        d[++k]=v[i];
    }


    int kk=k+1;
    for(i=n; i>=1; i--)
    {
        while (k>=kk && ordine(d[k-1], d[k], v[i])<=0) k--;
        d[++k]=v[i];
    }

    k--;

    g<<k<<"\n";

    //for (i=1; i<=k; i++) cout<<fixed<<setprecision(6)<<d[i].x<<" "<<d[i].y<<"\n";
    return 0;
}