#include <fstream>
#include <algorithm>
#include <iomanip>

using namespace std;

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

const int NMax = 120005;
int N,NStack;
int Stack[NMax];
pair < double, double > P [NMax];


int Sign(pair < double, double> A, pair < double, double >B, pair <double, double> C)
{
  return A.first * B.second + B.first * C.second + C.first * A.second - A.second * B.first - B.second * C.first - C.second * A.first;
}

bool Compare( pair < double, double> A, pair < double, double >B)
{
  return Sign(P[1],A,B) > 0;
}

void Read()
{
  fin >> N;
  for(int i = 1; i <= N; ++i)
    {
      double x,y;
      fin >> x >> y;
      P[i] = make_pair(x,y);
    }
  int Min = 1;
  for(int i = 2; i <= N; ++i)
    {
      if(P[i].second < P[Min].second || (P[i].second == P[Min].second && P[i].first < P[Min].first) )
        Min = i;
    }
  swap(P[1],P[Min]);
  sort(P + 2, P + N + 1,Compare);
}

void Solve()
{
  Stack[1] = 1; Stack[2] = 2;
  NStack = 2;
  for(int i = 3; i <= N; ++i)
    {
      while(NStack > 2 && Sign(P[Stack[NStack - 1]],P[Stack[NStack]], P[i] ) < 0)
        NStack--;
      Stack[++NStack] = i;
    }
}
void Print()
{
  fout << NStack << "\n";
  for(int i = 1; i <= NStack; ++i)
    fout << fixed << setprecision(6)<< P[Stack[i]].first << " " << P[Stack[i]].second << "\n";
}
int main()
{
    Read();
    Solve();
    Print();
    return 0;
}