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

using namespace std;

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

double X[maxn], Y[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]);
}

double semn (int i1, int i2, int i3) {
  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() {
  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);
  p = 1; ST[p] = PI;
  for (int i = 1; i <= N-1; i++) {
    while (p >= 2 and semn(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;
}