#include <cstdio>
#include <vector>
#include <iomanip>
#include <algorithm>
using namespace std;

#define x first
#define y second
#define sz size
#define add push_back
#define L S.sz()-1
#define erase pop_back

typedef double ld;
typedef pair <ld, ld> punct;
typedef vector <punct> poligon;

poligon P, S;
int n;

inline ld cross(punct A, punct B, punct C) {
    return (B.x - A.x) * (C.y - A.y) - (C.x - A.x) * (B.y - A.y);
}

inline bool cmp (punct A, punct B) {
    return cross(P[0], A, B) < 0;
}

int main() {
    freopen ("infasuratoare.in", "r", stdin);
    freopen ("infasuratoare.out", "w", stdout);
    scanf ("%d\n", &n);
    int pos = 0;
    for (int i = 0; i < n; ++i) {
        punct p;
        scanf ("%lf %lf", &p.x, &p.y);
        P.add(p);
        if (P[pos] > P[i])
            pos = i;
    }
    swap (P[pos], P[0]);
    poligon :: iterator it = P.begin();
    it++;
    sort(it, P.end(), cmp);
    S.add (P[0]);
    S.add (P[1]);
    for (int i = 2; i < n; ++i) {
        while (S.sz() > 1 && cross (S[L-1], S[L], P[i]) > 0) {
            S.erase();
        }
        S.add (P[i]);
    }
    printf ("%d\n", S.sz());
    for (int i = L; i >= 0; --i)
        printf ("%.9lf %.9lf\n", S[i].x, S[i].y);
    return 0;
}