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

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

const double eps = 1.0e-12;

struct POINT{
    double x, y;
};

POINT P[120005];
POINT LL;
int h[120005];

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

int ccw(POINT A, POINT B, POINT C){
    double cpp = cp(A, B, C);

    if(fabs(cpp) < eps)
        return 0;
    if(cpp >= eps)
        return 1;
    return -1;
}

bool cmp(POINT P1, POINT P2){
    return ccw(LL, P1, P2) >= 0;
}

int main()
{
    int n, i, top;
    double tx, ty;

    fin >> n;

    //LL sa contina punctul y minim si cu x minim

    fin >> tx >> ty;
    LL.x = tx;
    LL.y = ty;

    P[0] = LL;

    for(i = 1; i < n; ++i){
        fin >> tx >> ty;
        P[i].x = tx;
        P[i].y = ty;

        if(ty - LL.y <= -eps || (fabs(LL.y - ty) < eps && tx - LL.x <= -eps)){
            LL.x = tx;
            LL.y = ty;
            P[i] = P[0];
            P[0] = LL;
        }
    }

    sort(P + 1, P + n, cmp);

    P[n] = LL; //inchidere linie franta

    h[0] = 0;
    h[1] = 1;
    top = 1;
    i = 2;

    while(i <= n){
        if(ccw(P[h[top - 1]], P[h[top]], P[i]) > 0){
            h[++top] = i;
            i++;
        }
        else
            top--;
    }

    fout << top << "\n";

    fout << showpoint << fixed << setprecision(6);

    for(i = 0; i < top; ++i)
        fout << P[h[i]].x << " " << P[h[i]].y << "\n";

    fin.close();
    fout.close();
    return 0;
}