/**
  *  Worg
  */
#include <cstdio>
#include <vector>
#include <utility>
#include <algorithm>

#define x first
#define y second

FILE *fin = freopen("infasuratoare.in", "r", stdin); FILE *fout = freopen("infasuratoare.out", "w", stdout);

typedef std::pair<double, double > Point;

/*-------- Data --------*/
int n;
std::vector<Point > points;
/*-------- --------*/

void ReadInput() {
  scanf("%d", &n); points.resize(n);

  for(auto& point : points) {
    scanf("%lf%lf", &point.x, &point.y);
  }
}

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

std::vector<Point > ConvexHull(std::vector<Point > &points) {
  int n = (int)points.size();
  for(int i = 1; i < n; i++) {
    if(points[i] < points[0]) {
      std::swap(points[0], points[i]);
    }
  }

  std::sort(points.begin() + 1, points.end(), [&](Point &A, Point &B) {
    return CrossProduct(points[0], A, B) > 0;
  });

  std::vector<Point > convexHull; convexHull.push_back(points[0]);

  for(int i = 1; i < n; i++) {
    auto point = points[i];

    while(convexHull.size() > 1 && CrossProduct(convexHull[(int)convexHull.size() - 2], convexHull[(int)convexHull.size() - 1], point) < 0) {
      convexHull.pop_back();
    }
    convexHull.push_back(point);
  }

  return convexHull;
}

int main() {
  ReadInput();

  auto convexHull = ConvexHull(points);

  printf("%d\n", (int)convexHull.size());
  for(auto& point : convexHull) {
    printf("%.12f %.12f\n", point.x, point.y);
  }
  return 0;
}