#include <cstdio>
#include <algorithm>
#include <cmath>

using namespace std;

const int maxn = 120000;
const int INF = 1000000000;

double X[maxn], Y[maxn];
long double V[maxn];
int PI, IND[maxn], N, ST[maxn], p, l;

bool cmpf(int i, int j) {
  return (X[i] - X[PI]) * (Y[j] - Y[PI]) > (X[j] - X[PI]) * (Y[i] - Y[PI]);
}

bool right(int i, int j, int k)
{
    return (X[i] * (Y[j] - Y[k]) + X[j] * (Y[k] - Y[i]) + X[k] * (Y[i] - Y[j])) > 0;
}

int main() {
  freopen("infasuratoare.in", "r", stdin);
  freopen("infasuratoare.out", "w", stdout);
  scanf("%d\n", &N);
  X[0] = INF; Y[0] = INF; PI = 0;
  for (int i = 1; i <= N; i++) {
    scanf("%lf %lf", &X[i], &Y[i]);
    if (X[i] < X[PI] or (X[i] == X[PI] and Y[i] < Y[PI]))
      PI = i;
  }
  for (int i = 1; i <= N; i++) {
    if (i != PI)
      IND[++l] = i;
  }
  sort(IND + 1, IND + N, cmpf);
  ST[p = 1] = PI;
  for (int i = 1; i <= N-1; ++i) {
    while (p >= 2 && !right(ST[p - 1], ST[p], IND[i]) < 0)
      --p;
    ST[++p] = IND[i];
  }
  printf("%d\n", p);
  for (int i = 1; i <= p; ++i)
    printf("%lf %lf\n", X[ST[i]], Y[ST[i]]);
  return 0;
}