#include<bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pb push_back
#define ft first
#define sc second
#define ll long long
ifstream fin("infasuratoare.in"); ofstream fout("infasuratoare.out");



int n;
pair<double, double> p[120000];



double cross_product( pair<double, double> &p1, pair<double, double> &p2, pair<double, double> &p3 ){

return (p2.ft-p1.ft)*(p3.sc-p2.sc)-(p3.ft-p2.ft)*(p2.sc-p1.sc);

}








int main(){
fin>>n;

int p0=0;
for(int i=0; i<n; i++){
fin>>p[i].ft>>p[i].sc;
if(p[i].sc<p[p0].sc){
p0=i;
}
else{
    if(p[i].sc==p[p0].sc){
        if(p[i].ft<p[p0].ft){
            p0=i;
        }
    }
}

}



vector<pair<double, int> > g;

g.pb(mp(-100, p0) );

for(int i=0; i<n; i++){
    if(i!=p0){
        g.pb( mp(atan2( (p[i].sc-p[p0].sc), (p[i].ft-p[p0].ft )   ), i)    );

    }
}
sort(g.begin(), g.end());




for(int i=2; i<g.size(); i++){


    while( i>=2 && cross_product( p[g[i-2].sc ], p[g[i-1].sc ], p[g[i].sc ]    )<=0   ){
        g.erase(g.begin()+i-2+1, g.begin()+i-2+2 ); i--;
    }




}




fout<<g.size()<<"\n";
for(int i=0; i<g.size(); i++){
    fout<<fixed<<setprecision(9)<<p[g[i].sc ].ft<<" "<<p[g[i].sc ].sc<<"\n";
}

return 0;
}