#include <iostream>
#include <fstream>
#include <cmath>
#include <iomanip>
#include <algorithm>
using namespace std;

struct Point {
    double x, y;
};

#define nmax 120005
#define E 1e-12
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

int n;
Point A[nmax];

int i, len;
int st[nmax];
bool viz[nmax];

bool cmp(Point a, Point b) {
    if (a.y == b.y)
        return a.x < b.x;
    return a.y < b.y;
}

double det(Point O, Point A, Point B) {
    return (A.x - O.x) * (B.y - O.y) - (A.y - O.y) * (B.x - O.x);
}

void read() {
    fin >> n;
    for (i=1; i<=n; i++)
        fin >> A[i].x >> A[i].y;
}

void convex_hull() {
    sort(A+1, A+n+1, cmp);
    
    st[1] = 1, st[2] = 2, len = 2;
    viz[1] = viz[2] = true;
    
    for (i=1; i<=n; i++){
        while (len > 1 && det(A[st[len-1]], A[st[len]], A[i]) < E) viz[st[len--]] = false;
        st[++len]=i;
        viz[i] = true;
    }
    
    for (i=n-1; i>0; i--){
        if (viz[i]) continue;
        while(len > 1 && det(A[st[len-1]], A[st[len]], A[i]) < E)
            len--;
        st[++len]=i;
    }
    
    fout << len-1 << "\n";
    fout << setprecision(6) << fixed;
    for (i=1; i<len; i++)
        fout << A[st[i]].x << " " << A[st[i]].y << "\n";
    
}

int main() {
    
    read();
    convex_hull();
    
    return 0;
}