#include<cstdio>
#include<fstream>
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<bitset>
#include<deque>
#include<queue>
#include<set>
#include<map>
#include<cmath>
#include<cstring>
#include<ctime>
#include<cstdlib>
#include<unordered_map>

#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>
#define point pair<double,double>
#define all(x) (x).begin(), (x).end()
#define x first
#define y second

using namespace std;

const int nmax = 120005;

int n, i, cntA, cntB;
point p[nmax], a[nmax], b[nmax];

double cp(point a, point b, point c)
{
    return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
}

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

    fin >> n;
    for(i = 1; i <= n; i++)
        fin >> p[i].x >> p[i].y;

    sort(p + 1, p + n + 1);

    for(i = 1; i <= n; i++)
    {
        while(cntA >= 2 && cp(a[cntA - 1], a[cntA], p[i]) > 0)
            cntA--;
        a[++cntA] = p[i];

        while(cntB >= 2 && cp(b[cntB - 1], b[cntB], p[i]) < 0)
            cntB--;
        b[++cntB] = p[i];
    }

    fout << cntA + cntB - 2 << '\n';

    for(i = 1; i <= cntB; i++)
        fout << fixed << setprecision(12) << b[i].x << " " << b[i].y << '\n';

    for(i = cntA - 1; i > 1; i--)
        fout << fixed << setprecision(12) << a[i].x << " " << a[i].y << '\n';

    return 0;
}