#include <bits/stdc++.h>

using namespace std;

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

#define x first
#define y second

const int NMAX = 120005;

pair <double, double> v[NMAX];

int n, top, st[NMAX];

double det (pair <double, double> A, pair <double, double> B, pair <double, double> C)
{
    return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

bool cmp (pair <double, double> A, pair <double, double> B)
{
    return det(v[1], A, B) < 0;
}

int main()
{
    freopen("infasuratoare.out","w",stdout);
    fin >> n;
    for (int i=1; i<=n; i++)
    {
        fin >> v[i].x >> v[i].y;
        if (i > 1 && v[i] < v[1]) swap(v[1], v[i]);
    }
    sort(v+2,v+n+1,cmp);
   // for (int i=1; i<=n; i++)
        //cout << v[i].x << " " << v[i].y << "\n";
    st[1] = 1;
    st[2] = 2;
    top = 2;
    for (int i=3; i<=n; i++)
    {
        while (top >= 2 && det(v[st[top-1]], v[st[top]], v[i]) > 0) --top;
        st[++top] = i;
    }
    printf("%d \n", top);
    for (int i=top; i>=1; i--)
        printf("%.12f %.12f\n",v[st[i]].x,v[st[i]].y);
    return 0;
}