#include <bits/stdc++.h>
using namespace std;
using pt = pair<double,double>;
#define pb push_back
#define x first 
#define y second

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

int n;
vector<int>r;
vector<pt> v;

inline double det(pt a, pt b, pt c){
    return a.x*b.y + b.x*c.y + c.x*a.y - a.y*b.x - b.y*c.x - c.y*a.x;
}
bool sorttrig(pt a, pt b){
    return det(v[0], a, b) > 0;
}

int main(){
    fin >> n; v.resize(n); 
    for (int i = 0; i < n; i++)
        fin >> v[i].x >> v[i].y;

    int i = 0;
    for (int j = 1; j < n; j++)
        if (v[i] > v[j]) i = j;
    swap(v[i], v[0]);
    sort(v.begin() + 1, v.end(), sorttrig);

    r.resize(n); r[1] = 1; int k = 1;
    for (int i = 2; i < n; i++){
        while (k > 1 && det(v[r[k-1]], v[r[k]], v[i]) <= 0) k--;
        k++; r[k] = i;
    }
    fout << k + 1 << '\n' << fixed << setprecision(12);
    for (int i = 0; i <= k; i++) 
        fout << v[r[i]].x << ' ' << v[r[i]].y << '\n';

    return 0;
}