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

const double eps = 1.e-14;
int h[120010];
struct POINT{
    double x,y;
};
POINT LL;
vector<POINT> points;

bool cmp(POINT a, POINT b){
    if(fabs(a.y - b.y) <= eps)
        return a.x - b.x <= -eps;
    return a.y - b.y <= -eps;
}

int ccw(POINT a, POINT b, POINT c){
    double cp;
    cp = (b.x - a.x)*(c.y - b.y) - (b.y - a.y)*(c.x - b.x);
    if(fabs(cp) <= eps)
        return 0;
    if(cp >= eps)
        return 1;
    return -1;
}

bool My_sort(POINT a, POINT b){
    return ccw(LL, a, b) > 0;
}
int main()
{
    int i,n, top;
    double x,y;
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    scanf("%d", &n);
    for(i=1; i<=n; ++i){
        scanf("%lf%lf", &x, &y);
        points.push_back({x*1.0, y*1.0});
    }
    sort(points.begin(), points.end(), cmp);
    LL = points[0];
    sort(points.begin()+1, points.end(), My_sort);
    points.push_back(points[0]);
    h[0] = 0;
    h[1] = 1;
    top = 1;
    i = 2;
    while(i <= n){
        if(ccw(points[h[top-1]], points[h[top]], points[i]) > 0){
            h[++top] = i;
            ++i;
        }
        else
            --top;
    }
    printf("%d\n",top);
    for(i=0; i<top; ++i)
        printf("%.6lf %.6lf\n", points[h[i]].x, points[h[i]].y);
    return 0;
}