#include <fstream>
#define DMAX 120005
#include <algorithm>
#include <iomanip>

using namespace std;

int n, sf;

int st[DMAX], ind;

struct punct {
    double x, y;
};

punct v[DMAX];

double cross_product(punct A, punct B, punct C){
    return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

bool cmp(const punct &A, const punct &B){
    return cross_product(v[1], A, B) < 0;
}

int main()
{
    ifstream in("infasuratoare.in");
    ofstream out("infasuratoare.out");
    in>>n;
    ind = 1;
    for(int i = 1; i <= n; ++i){
        in>>v[i].x>>v[i].y;
        if(v[i].x < v[ind].x) ind = i;
        if(v[i].x == v[1].x && v[i].y < v[1].y) ind = i; 
    }
    swap(v[ind], v[1]);
    sort(v + 1, v + n + 1, cmp);
    st[++sf] = 1;
    st[++sf] = 2;
    for(int i = 3; i <= n; ++i){
        while(sf >= 2 && cross_product(v[st[sf-1]], v[st[sf]], v[i]) > 0)
            sf--;
        st[++sf] = i;
    }
    out<<sf<<"\n";
    for(int i = sf; i >= 1; --i){
        out<<fixed<<setprecision(9)<<v[st[i]].x<<" "<<v[st[i]].y<<"\n";
    }
    in.close();
    out.close();
    return 0;
}