#include <fstream>
#include <algorithm>
#include <cmath>

using namespace std;

const int MAXN = 120001;
const int INF = 1000000001;

double x[MAXN], y[MAXN];
long double V[MAXN];
int pi, ind[MAXN], n, st[MAXN], v, l, i;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

bool cmp(int i, int j) { // comparam tangentele
  return (x[j] - x[pi]) * (y[i] - y[pi]) < (x[i] - x[pi]) * (y[j] - y[pi]);
}

double semn (int i1, int i2, int i3) { // aria cu semn a triunghiului
  return x[i1] * y[i2] + x[i2] * y[i3] + x[i3] * y[i1] - y[i1] * x[i2] - y[i2] * x[i3] - y[i3] * x[i1];
}

int main() {
  fin >> n;
  x[0] = INF; y[0] = INF; pi = 0;
  for (i = 1; i <= n; i++) {
    fin >> x[i] >> y[i];
    if (x[i] < x[pi] or (x[i] == x[pi] and y[i] < y[pi]))
      pi = i; // punctul initial
  }
  for (i = 1; i <= n; i++) {
    if (i != pi)
      ind[++l] = i; // indicii celorlalte puncte
  }
  sort(ind + 1, ind + n, cmp); // Sortam vectorul de indici
  st[v = 1] = pi; // v - varful stivei
  for (i = 1; i <= n - 1; i++) {
    while (v >= 2 and semn(st[v - 1], st[v], ind[i]) < 0)
      v--;
    st[++v] = ind[i];
  }
  fout << v << '\n';
  for (i = 1; i <= v; i++)
    fout << x[st[i]] << ' ' << y[st[i]] << '\n';
  return 0;
}