#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
#define MAXN 120005

struct pc
{
    double x,y;
}act, v[MAXN];

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

bool cmp(pc A, pc B)
{
    return determinant(v[1], A, B) > 0;
}

int st[MAXN];
int n,i,j,mn,nrst;
int main()
{
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);
    scanf("%d", &n);
    for(i=1; i<=n; i++)
        scanf("%lf%lf", &v[i].x, &v[i].y);

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

    swap(v[1],v[mn]);
    sort(v+2, v+n+1, cmp);

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

        st[++nrst]=i;
    }

    printf("%d\n", nrst);
    for(i=1; i<=nrst; i++)
        printf("%lf %lf\n", v[st[i]].x, v[st[i]].y);

    return 0;
}