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

using namespace std;
const int nmax = 12e4;

struct Point {
    float x, y;
};

Point v[nmax];
int st[nmax], k = 0;

float det ( 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 );
}

bool cmp ( const Point &a, const Point &b ) {
    return det ( v[0], a, b ) < 0;
}

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

int main() {
    int n, ind = 0;

    fin >> n >> v[0].x >> v[0].y;
    for ( int i = 1; i < n; i++ ) {
        fin >> v[i].x >> v[i].y;
        if ( v[i].x > v[ind].x || ( v[i].x == v[ind].x && v[i].y > v[ind].y ) )
            ind = i;
    }

    swap ( v[0], v[ind] );
    sort ( v + 1, v + n, cmp );

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

    fout << k << '\n';
    for ( int i = k - 1; i >= 0; i-- )
        fout << fixed << setprecision ( 6 ) << v[st[i]].x << ' ' << v[st[i]].y << '\n';


    return 0;
}