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


#define Nmax 120010
#define PD pair<double, double>
#define mp make_pair
#define x first
#define y second

PD V[Nmax], Stack[Nmax], Convex[Nmax];
int N, K;

double Det(PD A, PD B, PD C)
{
    return A.x * (B.y - C.y) + B.x * (C.y - A.y) + C.x * (A.y - B.y);
}

void Add_Points()
{
    int StackSize = 0;
    Stack[StackSize ++] = V[1];
    Stack[StackSize ++] = V[2];
    for(int i = 3; i <= N; ++ i)
    {
        while(StackSize >= 2 && Det(Stack[StackSize - 2], Stack[StackSize - 1], V[i]) < 0) StackSize --;
        Stack[StackSize ++] = V[i];
    }
    for(int i = 0; i < StackSize - 1; ++ i) Convex[++ K] = Stack[i];
}

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", &V[i].x, &V[i].y);
    sort(V + 1, V + N + 1);
    Add_Points();
    reverse(V + 1, V + N + 1);
    Add_Points();
    printf("%i\n", K);
    for(i = 1; i <= K; ++ i) printf("%lf %lf\n", Convex[i].x, Convex[i].y);
    return 0;
}