#include <fstream>
#include <algorithm>
#include <iomanip>

using namespace std;

typedef pair < double, double > Point;

unsigned int N;
Point v[120001];

Point Stack[120001];
unsigned int pos, head;
unsigned int i;

unsigned int H;

inline double cross_product (const Point& A, const Point& B, const Point& C)
{
    return (B.first - A.first) * (C.second - A.second) - (B.second - A.second) * (C.first - A.first);
}

inline int cmp (const Point& p1, const Point& p2)
{
    return cross_product(v[1],p1,p2) < 0;
}

int main ()
{
    ifstream fin ("infasuratoare.in");
    fin >> N;
    for (i=1; i<=N; i++)
        fin >> v[i].first >> v[i].second;
    fin.close();
    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[1] = v[1];
    Stack[2] = v[2];
    head = 2;
    for (i=3; i<=N; i++)
    {
        while (head >= 2 && cross_product(Stack[head-1],Stack[head],v[i]) > 0)
            head--;
        head++;
        Stack[head] = v[i];
    }
    H = head;
    ofstream fout ("infasuratoare.out");
    fout << H << '\n';
    for (i=H; i>=1; i--)
    {
        fout << fixed << setprecision(9) << Stack[i].first << ' ' << Stack[i].second;
        fout << '\n';
    }
    fout.close();
    return 0;
}