#include <bits/stdc++.h>

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct Punct {
    double x, y;
} v[120002], st[120002];
int n, i, top;

static inline double Det(Punct p1, Punct p2, Punct p3) {
    return ((p2.x - p1.x) * (p3.y - p1.y) - (p3.x - p1.x) * (p2.y - p1.y));
}

static inline bool Cmp(Punct a, Punct b) {
    return (Det(v[1], a, b) > 0);
}

int main() {
    fin >> n;
    for(i = 1; i <= n; i++) fin >> v[i].x >> v[i].y;

    int poz = 1;
    for(int i = 2; i <= n; i++) {
         if(v[i].y < v[poz].y || (v[i].y == v[poz].y && v[i].x < v[poz].x)) poz = i;
    }

    swap(v[1], v[poz]);

    sort(v + 2, v + n + 1, Cmp);

    st[++top] = v[1];
    for(i = 2; i <= n + 1; i++) {
        while(top >= 2 && Det(st[top - 1], st[top], v[i]) < 0) top--;
        st[++top] = v[i];
    }

    fout << top - 1 << "\n";
    fout << fixed << setprecision(6);
    for(i = 1; i < top; i++) fout << st[i].x << " " << st[i].y << "\n";

    return 0;
}