#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;

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

typedef pair<double, double > punct;

punct v[120005];


double det(punct a, punct b, punct c) {
    return (b.x - a.x) * (c.y - a.y) - (c.x - a.x) * (b.y - a.y);
}
//
//double dist(punct a, punct b)
//{
//    int dx = a.x - b.x, dy = a.y - b.y;
//    return sqrt(dx * dx + dy * dy);
//}
//
//
//bool cmp2(punct a, punct b) {
//    return det({0,0}, a, b) < 0;
//}
//
//double X, Y;
//bool comp(punct a, punct b)
//{
//    return atan2(a.y - Y, a.x - X) > atan2(b.y - Y, b.x - X);
//}

int cadran(int x, int y) {
    if (x > 0 && y >= 0)
        return 1;
    if (x >= 0 && y < 0)
        return 4;
    if (y > 0 && x <= 0)
        return 2;
    return 3;
}



int det(int X1, int Y1, int X2, int Y2, int X3, int Y3) {
    return (X2 - X1) * (Y3 - Y1) - (X3 - X1) * (Y2 - Y1);
}
int cmp(const pair<int, int>& a, const pair<int, int>& b) {
    int c1 = cadran(a.first, a.second);
    int c2 = cadran(b.first, b.second);
    if (c1 != c2)
        return c1 < c2;
    else {
        int d = det(v[0].first, v[0].second, a.first, a.second, b.first, b.second);
        if (d != 0)
            return d < 0;
        else
            return a.first * a.first + a.second * a.second < b.first* b.first + b.second * b.second;
    }
}


int main()
{
    int n;
    fin >> n;

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

    //sortare tip 1
    int pos = 1;
    for (int i = 2; i <= n; i++) {
        if (v[i] < v[pos]) {
            pos = i;
        }
    }
    v[0] = v[pos];
    swap(v[1], v[pos]);

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

    //sortare tip 2

    //sort(v1 + 1, v1 + 1 + n, cmp);


    //for (int i = 1; i <=n; i++) {
    //    cout << v[i].x << ' ' << v[i].y  << '\n';
    //}



    vector<punct> S(120005);
    S[1] = v[1];
    S[2] = v[2];

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

    }
    fout << head << '\n';
    for (int i = head; i >= 1; i--) {
        cout << fixed << setprecision(6) << S[i].x << ' ' << S[i].y << '\n';
    }

    return 0;
}