#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>
#define x first
#define y second

using namespace std;

const int nmx = 120002;

int n;
pair <double,double> v[nmx];
vector <pair<double,double> > fin;

float determinant(pair <double,double> p1, pair <double,double> p2, pair <double,double> p3){
    return (p2.x-p1.x)*(p3.y-p1.y)-(p2.y-p1.y)*(p3.x-p1.x);
}

struct Cmp {
    bool operator () (pair<double,double> a, pair <double,double> b){
        return determinant(v[1],a,b) > 0;
    }
} cmp;

int main(){
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);
    scanf("%d", &n);
    for(int i = 1; i <= n; ++i)
        scanf("%lf %lf", &v[i].x, &v[i].y);
    int pmin = 1;
    for(int i = 2; i <= n; ++i)
        if(v[i] < v[pmin])
            pmin = i;
    swap(v[1],v[pmin]);
    sort(v+2,v+n+1,cmp);
    for(int i = 1; i <= n; ++i){
        while(fin.size() >= 2 && determinant(fin[fin.size()-2],fin[fin.size()-1],v[i]) < 0)
            fin.pop_back();
        fin.push_back(v[i]);
    }
    printf("%d\n", fin.size());
    for(vector<pair<double,double> >::iterator it = fin.begin(); it != fin.end(); ++it)
        printf("%f %f\n", it->first, it->second);
    return 0;
}