#include<algorithm>
#include<bitset>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<deque>
#include<fstream>
#include<iomanip>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<vector>

using namespace std;

#ifdef HOME
const string inputFile = "input.txt";
const string outputFile = "output.txt";
#else
const string problemName = "infasuratoare";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";
#endif

const int NMAX = 120000 + 5;

struct point {
    double x, y;

    bool operator<(const point &B) const {
        if(x == B.x)
            return y < B.y;
        return x < B.x;
    }
};

int N, M;
point P[NMAX];
point H[NMAX];

double cp(point A, point B, point C) {
    return (A.x - C.x) * (B.y - C.y) - (B.x - C.x) * (A.y - C.y);
}

struct cmp {
    bool operator()(const point &A, const point &B) const {
        return cp(A, B, P[1]) > 0;
    }
};

int main() {
    int i;

#ifndef ONLINE_JUDGE
    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);
#endif

    scanf("%d", &N);

    for(i = 1; i <= N; i++) {
        scanf("%lf%lf", &P[i].x, &P[i].y);
        if(P[i] < P[1])
            swap(P[i], P[1]);
    }

    sort(P + 2, P + N + 1, cmp());

    for(i = 1; i <= N; i++) {
        while(M >= 2 && cp(H[M - 1], H[M], P[i]) < 0)
            M--;

        H[++M] = P[i];
    }

    printf("%d\n", M);

    for(i = 1; i <= M; i++)
        printf("%.12f %.12f\n", H[i].x, H[i].y);

    return 0;
}