#include <bits/stdc++.h>

using namespace std;

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


struct Punct{
    long double x, y;
    bool operator < (const Punct A) const{
        if(A.y == y)
            return x < A.x;
        return y < A.y;
    }
};

const int MaxN = 120004;
int n, st[MaxN], top, inclus[MaxN];
Punct a[MaxN];
vector<int>sol;

long double Dreapta(Punct A, Punct B, Punct C){
    long double a = B.y - A.y;
    long double b = A.x - B.x;
    long double c = A.x * (A.y - B.y) + A.y * (B.x - A.x);
    return a * C.x + b * C.y + c;
}

void Solve(){
    top = 1;
    st[top] = 1;
    inclus[1] = 1;
    for(int i = 2; i <= n; i++){
        ///scot din stiva elemente cat timp functia st[top - 1] si st[top] impreuna cu a[i] > 0
        while(top > 1 && Dreapta(a[st[top-1]], a[st[top]], a[i]) > 0){
            inclus[st[top]] = 0;
            top--;
        }
        st[++top] = i;
        inclus[i] = 1;
    }
    for(int i = 1; i <= top; i++)
        sol.push_back(st[i]);

    inclus[1] = 0;
    top = 1;
    st[1] = n;
    for(int i = n - 1; i >= 1; i--)
        if(!inclus[i]){
        ///scot din stiva elemente cat timp functia st[top - 1] si st[top] impreuna cu a[i] > 0
        while(top > 1 && Dreapta(a[st[top-1]], a[st[top]], a[i]) > 0){
            inclus[st[top]] = 0;
            top--;
        }
        st[++top] = i;
        inclus[i] = 1;
    }
    for(int i = 2; i <= top; i++)
        sol.push_back(st[i]);
}

void Afis(){
    sol.pop_back();
    fout << sol.size() << "\n";
    for(auto i : sol)
        fout << fixed << setprecision(12) << a[i].x << " " << a[i].y << "\n";
}

int main()
{
    fin >> n;
    for(int i = 1; i <= n; i++)
        fin >> a[i].x >> a[i].y;
    sort(a + 1, a + n + 1);
    Solve();
    Afis();
    return 0;
}