#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <algorithm>
using namespace std;


#define nmax 120010
#define x first
#define y second
#define dd pair<double, double>

dd A[nmax], st[nmax];
int r, N;

struct cmp
{
    bool operator () (const dd &A, const dd &B) const
    {
        if(A.y < B.y) return 1;
        if(A.y > B.y) return 0;
        if(A.x < B.x) return 1;
        return 0;
    };
};

int semnDet(dd a, dd b, dd c)
{
    double A = a.y - b.y, B = b.x - a.x, C = a.x * b.y - a.y * b.x;
    return (A * c.x + B * c.y + C) < 0;
}

void ConvexHull()
{
     int i;
     st[++r] = A[1];
     st[++r] = A[2];
     for(i = 3; i <= N; i++)
     {
           while(r >= 2 && semnDet(st[r - 1], st[r], A[i])) r--;
           st[++r] = A[i];
     }
     for(i = N - 1; i; i--)
     {
           while(r >= 2 && semnDet(st[r - 1], st[r], A[i])) r--;
           st[++r] = A[i];
     }
     r --;
     printf("%i\n", r);
     for(i = 1; i <= r; i++) printf("%lf %lf\n", st[i].x, st[i].y);
}

int main()
{
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);
    int i;
    scanf("%i", &N);
    for(i = 1; i <= N; i++) scanf("%lf %lf", &A[i].x, &A[i].y);
    sort(A + 1, A + N + 1, cmp());
    ConvexHull();
    return 0;
}