#include <bits/stdc++.h>
#define pb push_back

using namespace std;

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

void debug_out() { cerr << '\n'; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) { cerr << " " << H; debug_out(T...);}
#define dbg(...) cerr << #__VA_ARGS__ << " ->", debug_out(__VA_ARGS__)
#define dbg_v(x, n) do{cerr<<#x"[]: ";for(int _=0;_<n;++_)cerr<<x[_]<<" ";cerr<<'\n';}while(0)
#define dbg_ok cerr<<"OK!\n"

typedef pair<int,int> pii;
typedef long long int ll;
typedef long double ld;

const int DMAX = 12e4+10;

struct nume{
    ld x,y;
};

vector <nume> vec;

nume V[DMAX];

int n;

ld fct(nume p,nume a,nume b){
    return (a.x-p.x)*(b.y-p.y)-(a.y-p.y)*(b.x-p.x);
}

inline bool operator<(nume x,nume y){
    return fct(V[1],x,y)<0;
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int t,i,j;

    fin>>n;
    for(i=1;i<=n;i++){
        fin>>V[i].x>>V[i].y;
        if(V[i].x < V[1].x || (V[i].x == V[1].x && V[i].y > V[1].y))
            swap(V[i],V[1]);
    }
    sort(V+2,V+n+1);
    vec.pb(V[1]);
    vec.pb(V[2]);
    for(i=3;i<=n;i++){
        while(vec.size() > 2 && fct(vec[vec.size()-1],vec[vec.size()-2],V[i]) <= 0)
            vec.pop_back();
        vec.pb(V[i]);
    }
    fout<<vec.size()<<'\n';
    reverse(vec.begin(),vec.end());
    for(auto& it:vec)
        fout<<fixed<<setprecision(7)<<it.x<<' '<<it.y<<'\n';

    return 0;
}