#include <bits/stdc++.h>
using namespace std;
#define NMAX 120005

struct point {
    double x, y;
} v[NMAX], c;

int n, Stack[NMAX], cnt;

int crossProduct(point a, point b, point c) {
    double cross = (a.x * b.y) - (a.y * b.x) + (b.x * c.y) - (b.y * c.x) + (c.x * a.y) - (c.y * a.x);

    if(cross > 0) return 1;
    if(!cross   ) return 0;
    return -1;
}

bool cmp(point a, point b) {
    if(a.x == c.x && a.y == c.y) {
        return true;
    } else if(b.x == c.x && b.y == c.y) {
        return false;
    }
    return crossProduct(a, b, c) > 0;
}

void read() {
    scanf("%d%lf%lf", &n, &c.x, &c.y);
    v[1] = c;

    for(int i = 2; i <= n; ++i) {
        scanf("%lf%lf", &v[i].x, &v[i].y);

        if((v[i].x == c.x && v[i].y < c.y) || (v[i].x < c.x)) {
            c = v[i];
        }
    }
}

void solve() {
    sort(v + 1, v + 1 + n, cmp);

    for(int i = 1; i <= n; ++i) {
        while(cnt >= 2 && crossProduct(v[Stack[cnt - 1]], v[Stack[cnt]], v[i]) <= 0) {
            --cnt;
        }
        Stack[++cnt] = i;
    }
}

void print() {
    printf("%d\n", cnt);
    for(int i = 1; i <= cnt; ++i) {
        printf("%lf %lf\n", v[Stack[i]].x, v[Stack[i]].y);
    }
}

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

    read();
    solve();
    print();
    return 0;
}