#include <bits/stdc++.h>
using namespace std;

#define ll unsigned long long
#define fast_read ios::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL)
#define x first
#define y second
const int maxn = 12e4;
const int maxm = 2e5;
const int mod = 666013;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
int n, k;
typedef pair<double, double> Point;
Point primul;
Point v[maxn + 2], st[maxn + 2];
void read(){
   fin >> n;
   for(int i = 1; i <= n; ++i) fin >> v[i].x >> v[i].y;
}
double arie(Point& a, Point& b, Point& c){
    return (b.x - a.x) * (c.y - a.y) - (c.x - a.x) * (b.y - a.y);
}
bool cmp(Point p1, Point p2){   
    return arie(v[1], p1, p2) < 0;
}
void convex_hull(){
    int pos = 1;
    for(int i = 2; i <= n; ++i)
        if(v[i] < v[pos])
            pos = i;
    swap(v[pos], v[1]);
    sort(v + 2, v + n + 1, cmp);
    st[++k] = v[1];
    st[++k] = v[2];
    for(int i = 3; i <= n; ++i){
        while(k >= 2 && (arie( st[k - 1], st[k], v[i]) > 0))
            k--;
        st[++k] = v[i];
    }
}
void write(){
    fout << fixed;
    fout << k << "\n";
    for(int i = k; i >= 1; --i)
        fout << setprecision(12) << st[i].x << " " << st[i].y << "\n";
}
int main(){
    read();
    convex_hull();
    write();
    return 0;
}
/*
task:

*/