#include<cstdio>
#include<fstream>
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<bitset>
#include<deque>
#include<queue>
#include<set>
#include<map>
#include<cmath>
#include<cstring>
#include<ctime>
#include<cstdlib>
#include<unordered_map>

#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>
#define point pair<double,double>
#define all(x) (x).begin(), (x).end()
#define x first
#define y second

using namespace std;

const int nmax = 120005;

int n, i, mini, cnt;
point p[nmax], st[nmax];

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

struct cmp
{
    bool operator () (point a, point b) const
    {
        return cp(p[1], a, b) < 0;
    }
};

int main()
{
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);

    scanf("%d", &n);

    mini = 1;
    for(i = 1; i <= n; i++)
    {
        scanf("%lf%lf", &p[i].x, &p[i].y);
        if(p[i] < p[mini]) mini = i;
    }

    swap(p[1], p[mini]);
    sort(p + 2, p + n + 1, cmp());

    for(i = 1; i <= n; i++)
    {
        while(cnt >= 2 && cp(st[cnt - 1], st[cnt], p[i]) > 0) cnt--;
        st[++cnt] = p[i];
    }

    printf("%d\n", cnt);
    for(i = cnt; i; i--)
        printf("%.12f %.12f\n", st[i].x, st[i].y);

    return 0;
}