#include <fstream>
#include <vector>
#include <bitset>
#include <queue>
#include <algorithm>
#include <utility>
#include <cstring>
#include <string>
#include <stack>
#include <deque>
#include <iomanip>
#include <set>
#include <map>
#include <cassert>
#include <ctime>
#include <list>
#include <iomanip>

#define x first
#define y second

using namespace std;

string file = "infasuratoare";

ifstream cin( (file + ".in").c_str() );
ofstream cout( (file + ".out").c_str() );

const int MAXN = 120005;
const int oo = 0x3f3f3f3f;

typedef pair<double, double> pdd;
const inline int min(const int &a, const int &b) { if( a > b ) return b;   return a; }
const inline int max(const int &a, const int &b) { if( a < b ) return b;   return a; }
const inline void Get_min(int &a, const int b)    { if( a > b ) a = b; }
const inline void Get_max(int &a, const int b)    { if( a < b ) a = b; }


pdd P[MAXN];
int N, p, k, st[MAXN];
double X = oo, Y = oo;

struct ClassComp {
    inline bool operator () (const pdd &a, const pdd &b) const {
        return (a.x - X) * (b.y - Y) < (b.x - X) * (a.y - Y);
    }
};

inline bool Match(pdd x, pdd y, pdd z) {
/*
    double  a = z.y - x.y,
            b = x.x - z.x,
            c = z.x*x.y - x.x*z.y;
    double x1 = a*x.x + b*x.y + c;
    double x2 = a*y.x + b*y.y + c;
    double sol = x1 * x2;
*/
    double sol = x.x * y.y + y.x * z.y + z.x * x.y - x.y * y.x - y.y * z.x - z.y * x.x;
    return sol > 0;
}

int main() {
    cin >> N;
    for(int i = 1 ; i <= N ; ++ i) {
        cin >> P[i].x >> P[i].y;
        if(P[i].x < X || ( P[i].x == X && P[i].y < Y) ) {
            X = P[i].x;
            Y = P[i].y;
            p = i;
        }
    }
    swap(P[p], P[N]);
    p = N;
    sort(P + 1, P + N, ClassComp());
    st[ ++ k ] = p;
    for(int i = 1 ; i <= N ; ++ i) {
        if(p == i)
            continue;
        while( k >= 2 && Match(P[st[k-1]], P[st[k]], P[i]))
            -- k;
        st[++k] = i;
    }
    cout << k << '\n';
    cout << fixed << setprecision(6);
    for(int i = k ; i ; -- i)
        cout << P[st[i]].x << ' ' << P[st[i]].y << '\n';
    cin.close();
    cout.close();
    return 0;
}