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


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

PD V[Nmax], Stack[Nmax];
int N, Head;

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

int Cmp(PD A, PD B)
{
    return Cross_Product(V[1], A, B) < 0;
}

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);
    int Pos = 1;
    for(i = 2; i <= N; i++)
        if(V[i] < V[Pos])
            Pos = i;
    swap(V[1], V[Pos]);
    sort(V + 2, V + N + 1, Cmp);
    Stack[++Head] = V[1];
    Stack[++Head] = V[2];
    for(i = 3; i <= N; i++)
    {
        while(Head >= 2 && Cross_Product(Stack[Head - 1], Stack[Head], V[i]) > 0) Head --;
        Stack[++Head] = V[i];
    }
    printf("%i\n", Head);
    for(i = Head; i; i--) printf("%.9lf %.9lf\n", Stack[i].x, Stack[i].y);
    return 0;
}