#include <bits/stdc++.h>

using namespace std;

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


const int Nmax = 120005;


int n, st[Nmax], top;

struct P
{
    long double x, y;
};

P a[Nmax];

bool viz[Nmax];


inline bool CMP(const P A, const P B)
{
    if(A.y == B.y)
        return A.x < B.x;
    return A.y < B.y;
}

inline bool D(long double x, long double y, long double x1, long double y1, long double x2, long double y2)
{
    long double p;
    p = x * y1 + x2 * y + x1 * y2 - x2 * y1 - x * y2 - x1 * y;
    return (p < 0);
}

int main()
{
    fin >> n;
    for(int i = 1 ; i <= n ; i++)
        fin >> a[i].x >> a[i].y;
    sort(a + 1, a + n + 1, CMP);
    top = 2;
    st[1] = 1;
    st[2] = 2;
    viz[2] = true;
    for(int i = 3 ; i <= n ; i++)
    {
        while(top && D(a[i].x, a[i].y, a[st[top - 1]].x, a[st[top - 1]].y, a[st[top]].x, a[st[top]].y ))
        {
            viz[st[top]] = false;
            --top;
        }
        ++top;
        st[top] = i;
        viz[i] = true;
    }
    for(int i = n ; i >= 1 ; i--)
        if(!viz[i])
        {
            while(top && D(a[i].x, a[i].y, a[st[top - 1]].x, a[st[top - 1]].y, a[st[top]].x, a[st[top]].y ))
            {
                viz[st[top]] = false;
                --top;
            }
            ++top;
            st[top] = i;
            viz[i] = true;
        }
    fout << (top - 1) << "\n";
    for(int i = 1 ; i < top ; i++)
        fout << fixed << setprecision(12) << a[st[i]].x << " " << a[st[i]].y << "\n";
    fin.close();
    fout.close();
    return 0;
}