#include <algorithm>
#include <cmath>
#include <cstdio>

using namespace std;

const int MAXN = 120000;
const int INF = 1000000000;

double x[MAXN], y[MAXN];
int pinitial, ind[MAXN], n, st[MAXN], p, l;

bool cmpf(int i, int j) {
    return (x[i] - x[pinitial]) * (y[j] - y[pinitial]) > (x[j] - x[pinitial]) * (y[i] - y[pinitial]);
}

double semn(int i1, int i2, int i3) {
    return x[i1] * y[i2] + x[i2] * y[i3] + x[i3] * y[i1] - y[i1] * x[i2] - y[i2] * x[i3] - y[i3] * x[i1];
}

int main() {
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);
    scanf("%d\n", &n);
    x[0] = INF;
    y[0] = INF;
    pinitial = 0;
    for (int i = 1; i <= n; i++) {
        scanf("%lf %lf", &x[i], &y[i]);
        if (y[i] < y[pinitial])
            pinitial = i;
    }
    for (int i = 1; i <= n; i++)
        if (i != pinitial)
            ind[++l] = i;
    sort(ind + 1, ind + n, cmpf);
    p = 1;
    st[p] = pinitial;
    for (int i = 1; i <= n - 1; ++i) {
        while (p >= 2 and semn(st[p - 1], st[p], ind[i]) < 0)
            --p;
        st[++p] = ind[i];
    }
    printf("%d\n", p);
    for (int i = 1; i <= p; ++i)
        printf("%lf %lf\n", x[st[i]], y[st[i]]);
    return 0;
}