#include <bits/stdc++.h>

#define x first
#define y second

using namespace std;

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

typedef pair<double, double> point;

point v[120005],s[120005];

int n,i,j,mini,dr;

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

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

int main()
{
    fin >> n;

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

    mini = 1;

    for (i = 2;i <= n;i++)
        if (v[i] < v[mini])
            mini = i;

    swap(v[mini],v[1]);

    sort(v+2,v+n+1,cmp);

    s[1] = v[1];
    s[2] = v[2];
    dr = 2;

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

    fout << fixed << dr << setprecision(6) << "\n";

    for (i = dr;i >= 1;i--)
        fout << s[i].x << " " << s[i].y << "\n";

    return 0;
}