#include <cstdio>
#include <iostream>
#include <algorithm>
#include <utility>
#include <stack>
#include <iomanip>
#include <cmath>
#include <cstdlib>

using namespace std;

#define DIM 120005

struct punct {
    double x, y;
} V[DIM], pct;

punct MySt[DIM];
int vf;
int N;

double CrossProduct(punct a, punct b, punct c);
bool cmp(punct a, punct b);

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

    scanf("%d\n", &N);

    int pos;

    pct.x = 2e9;
    pct.y = 2e9;

    for(int i = 1; i <= N; ++i) {
        scanf("%lf %lf\n", &V[i].x, &V[i].y);

        if(pct.y > V[i].y) {
            pct = V[i];
            pos = i;
        }
        else {
            if(pct.y == V[i].y && pct.x > V[i].x) {
                pct = V[i];
                pos = i;
            }
        }
    }

    swap(V[1], V[pos]);
    sort(V + 2, V + 1 + N, cmp);

    MySt[vf++] = V[1];
    MySt[vf] = V[2];

    for(int i = 3; i <= N; ++i) {
        while(vf >= 1 && CrossProduct(MySt[vf - 1], MySt[vf], V[i]) > 0) {
            --vf;
        }
        MySt[++vf] = V[i];
    }

    cout << vf + 1 << '\n';

    while(vf >= 0) {
        cout << setprecision(9) << fixed << MySt[vf].x << ' ' << MySt[vf].y << '\n';
        --vf;
    }

    return 0;
}

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

bool cmp(punct a, punct b) {
    return (CrossProduct(V[1], a, b) < 0);
}