#include <cstdio>
#include <algorithm>
#include <fstream>
#include <iomanip>

using namespace std;

#define x first
#define y second

typedef pair<double, double> point;

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

#define MAX_N 120005

int n;
point v[MAX_N];

point stack[MAX_N];
int k;

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

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

int cmp(const point& p1, const point& p2) {
    return cross_product(v[1], p1, p2) < 0;
}

void sort_points() {
    int posmin = 1;
    for( int i = 2; i <= n; ++i )
        if( v[i] < v[posmin] )
            posmin = i;
    swap( v[1], v[posmin] );
    sort( v + 2, v + n + 1, cmp );
}

void convex_hull() {
    sort_points();

    stack[1] = v[1];
    stack[2] = v[2];
    k = 2;
    for( int i = 3; i <= n; ++i ) {
        while (k >= 2 && cross_product(stack[k - 1], stack[k], v[i]) > 0)
            --k;
        stack[++k] = v[i];
    }
}

void write() {
    fout << fixed;
    fout << k << "\n";
    for (int i = k; i >= 1; --i)
        fout << setprecision(9) << stack[i].x << " " << stack[i].y << "\n";
}

int main() {
    read();
    convex_hull();
    write();
}