#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define x first
#define y second
#define pb push_back
#define mp make_pair
#define pi pair<ll, ll>
#define sz(x) (int)((x).size())
#define all(a) (a).begin(), (a).end()

/*const ll maxn = 1e5;
int f[maxn],nf[maxn],inv[maxn];
const int M=998244353;
void init(){
    inv[1]=1; for (int i=2;i<maxn;i++) inv[i]=M-1ll*(M/i)*inv[M%i]%M;
    f[0]=nf[0]=1; for (int i=1;i<maxn;i++) f[i]=1ll*f[i-1]*i%M,nf[i]=1ll*nf[i-1]*inv[i]%M;
}
int C(int x,int y){return 1ll*f[x]*nf[y]%M*nf[x-y]%M;} */

const ll mod = 1e9+7;
ll n, k, m, mi, ma;
const ll N = 2e5;
typedef pair<double, double> point;
vector<point> v(N), a(N);

double cross_product(point a, point b, point c){
	return (b.x - a.x)*(c.y - a.y) - (b.y - a.y)*(c.x - a.x);
}

bool cmp(point p1, point p2){
	return cross_product(v[0], p1, p2) < 0;
}

void sort_points(){
	ll pos = 0;
	for(int i = 1; i<n; i++) if(v[i] < v[pos]) pos = i;
	swap(v[0], v[pos]);
	sort(v.begin() + 1, v.begin() + n, cmp);
}



void solve(){
	
	cin >> n;
	for(int i = 0; i<n; i++){
		cin >> v[i].x >> v[i].y;
	}
	sort_points();
	point a[n + 5];
	ll head = 1;
	a[0] = v[0];
	a[1] = v[1];
	for(int i = 2; i<n; i++){
		while(head >= 1 && cross_product(a[head - 1], a[head], v[i]) > 0) head--;
		a[++head] = v[i];	
	}
	cout << head << "\n";
	for(int i = head; i>=0; i--){
		cout << setprecision(9) << fixed <<  a[i].x << " " << a[i].y << "\n";
	}
	

}

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

	//init();
	
	int t=1;
	//cin >> t;
	while(t--) solve();
	
	return 0;
}