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

struct pc
{
    double x, y;
}crt;

vector<pc> v;
int st[MAXN];
int n, nrSt;

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[0], A, B) > 0;
}

int main()
{
    int i, mn = 0;
    
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);
    
    scanf("%d", &n);
    for(i=1; i<=n; i++)
    {
        scanf("%lf %lf", &crt.x, &crt.y);
        v.push_back( crt );
    }
    
    for(i=1; 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[0], v[mn]);
    sort(v.begin() +1, v.end(), cmp);
    
    for(i=0; 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;
}