#include <bits/stdc++.h>
using namespace std;
#define x first
#define y second
#define Point pair<double,double>
int n;
#define LMAX 120001
Point v[LMAX],H[LMAX];
double det(const Point &A,const Point &B,const Point &C){
    /// Sarrus
    return (A.x*B.y+B.x*C.y+C.x*A.y)-(A.y*B.x+B.y*C.x+C.y*A.x);
}

bool cmp(const Point &A,const Point &B){
    return det(v[1],A,B)<0;
}
int main()
{
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;++i){
        scanf("%lf%lf",&v[i].x,&v[i].y);
        if(i>=2&&v[i]<v[1]) swap(v[i],v[1]);
    }
    sort(v+2,v+n+1,cmp);
    H[1]=v[1];
    int top=1;
    for(int i=2;i<=n;++i){
        while(top>=2&&det(H[top-1],H[top],v[i])>0)
            --top;
        H[++top]=v[i];
    }
    printf("%d\n", top);
    for(int i=top;i>=1;--i)
        printf("%0.12f %0.12f\n", H[i].x,H[i].y);
    return 0;
}