#include <stdio.h>
#include <algorithm>
#include <vector>
#define Point pair<double, double>
#define x first
#define y second
#define mp make_pair
#define MAXN 120005
using namespace std;

int n;
Point p[MAXN];

double crossProduct(Point A, Point B, Point C) {
    // AB x AC
    double x1 = B.x - A.x, y1 = B.y - A.y;
    double x2 = C.x - A.x, y2 = C.y - A.y;

    return x1 * y2 - x2 * y1;
}

bool Comp(Point A, Point B) {
    return crossProduct(p[1], A, B) > 0;
}

int main()
{
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);

    scanf("%d", &n);

    int lmost = 1;
    for(int i = 1; i <= n; i++) {
        scanf("%lf %lf", &p[i].x, &p[i].y);
        if(p[i].x < p[lmost].x || (p[i].x == p[lmost].x && p[i].y < p[lmost].y))
            lmost = i;
    }

    swap(p[1], p[lmost]);
    sort(p + 2, p + n + 1, Comp);

    vector<Point> H;
    H.push_back(p[1]);

    for(int i = 2; i <= n; i++) {
        while(H.size() > 1 && crossProduct(H[H.size() - 2], H.back(), p[i]) < 0) H.pop_back();
        H.push_back(p[i]);
    }

    printf("%d\n", H.size());
    for(auto p: H)
        printf("%.15f %.15f\n", p.x, p.y);

    return 0;
}