#include <bits/stdc++.h>
#define NMAX 120005
#define x first
#define y second

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

typedef pair<double,double> Point;

int n,head;
Point s[NMAX],v[NMAX];

inline double crossProduct(Point A, Point B, Point C) {
    B.x-=A.x;
    B.y-=A.y;
    C.x-=A.x;
    C.y-=A.y;
    return B.x*C.y-B.y*C.x;
}

bool cmp(Point a, Point b) {
    return crossProduct(v[1],a,b) < 0;
}

void sortPoints() {
    int pos=1;
    for(int i=2;i<=n;i++) if(v[i]<v[pos]) pos=i;
    swap(v[1],v[pos]);
    sort(v+2,v+n+1,cmp);
}

void convexHull() {
    s[1]=v[1];
    s[2]=v[2];

    head=2;
    for(int i=3;i<=n;i++) {
        while(head>=2&&crossProduct(s[head-1],s[head],v[i])>0) {
            head--;
        }
        s[++head]=v[i];
    }
}

int main()
{
    fin>>n;
    for(int i=1;i<=n;i++) fin>>v[i].x>>v[i].y;
    sortPoints();
    convexHull();

    fout<<fixed;
    fout<<head<<'\n';
    while(head) {
        fout<<setprecision(9)<<s[head].x<<' '<<s[head].y<<'\n';
        head--;
    }
    return 0;
}