#include <bits/stdc++.h>
#define point pair<float, float>
#define x first
#define y second

using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n, head = 2;
point v[120005], st[120005];

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

double cross_product(point A, point B, point C)
{
  return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

bool cmp(point p1, point p2)
{
  return cross_product(v[1], p1, p2) < 0;
}

void prepare()
{
  int pos = 1;
  for(int i = 2;i <= n;++i)
    if(v[i] < v[pos])
      pos = i;
  swap(v[1], v[pos]);
  sort(v + 2, v + n + 1, cmp);
}

void Solve()
{
  prepare(); 
  st[1] = v[1], st[2] = v[2];
  for(int i = 3;i <= n;++i)
    {
      while(head >= 2 && cross_product(st[head - 1], st[head], v[i]) > 0)
        --head;
      st[++head] = v[i];
    }
  g<<setprecision(12)<<fixed;
  g<<head<<'\n';
  for(int i = head;i >= 1;--i)
      g<<st[i].x<<" "<<st[i].y<<'\n'; 
}

int main()
{
  Read();
  Solve();
  return 0;
}