#include<cstdio>
#include<string>
#include<algorithm>

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

typedef pair<double, double> PDD;
const int NMAX = 120000 + 5;

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

double cp(PDD A, PDD B, PDD C) {
    return (A.first - C.first) * (B.second - C.second) - (A.second - C.second) * (B.first - C.first);
}

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

int main() {
    int i;

    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);

    scanf("%d", &N);

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

    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].first, H[i].second);

    return 0;
}