#include <fstream>
#include <iostream>
#include <vector>
#include <bitset>
#include <string.h>
#include <algorithm>
#include <iomanip>
#include <math.h>
#include <time.h>
#include <stdlib.h>
#include <set>
#include <map>
#include <string>
#include <queue>
#include <deque>

using namespace std;

const char infile[] = "infasuratoare.in";
const char outfile[] = "infasuratoare.out";

ifstream fin(infile);
ofstream fout(outfile);

const int MAXN = 120005;
const int oo = 0x3f3f3f3f;

typedef vector<int> Graph[MAXN];
typedef vector<int> :: iterator It;

const inline int min(const int &a, const int &b) { if( a > b ) return b;   return a; }
const inline int max(const int &a, const int &b) { if( a < b ) return b;   return a; }
const inline void Get_min(int &a, const int b)    { if( a > b ) a = b; }
const inline void Get_max(int &a, const int b)    { if( a < b ) a = b; }

int N, ind = 1, top;
pair<double, double> P[MAXN], st[MAXN];

inline double crossPoint(pair<double, double> a, pair<double, double> b, pair<double, double> c) {
    return (b.first - a.first) * (c.second - a.second) - (b.second - a.second) * (c.first - a.first);
}

struct classComp {
    inline bool operator () (const pair<double, double> &a, const pair<double, double> &b) const {
        return crossPoint(P[1], a, b) < 0;
    }
};

inline void convexHull() {
    st[++ top] = P[1];
    st[++ top] = P[2];
    for(int i = 3 ; i <= N ; ++ i) {
        while(top > 1 && crossPoint(st[top - 1], st[top], P[i]) > 0)
            -- top;
        st[++ top] = P[i];
    }
    fout << top << '\n' << fixed << setprecision(6);
    for( ; top ; -- top)  fout << st[top].first << ' ' << st[top].second << '\n';
}

int main() {
    fin >> N;
    for(int i = 1 ; i <= N ; ++ i) {
        fin >> P[i].first >> P[i].second;
        if(P[ind] > P[i])
            ind = i;
    }
    swap(P[ind], P[1]);
    sort(P + 2, P + N + 1, classComp());
    convexHull();
    fin.close();
    fout.close();
    return 0;
}